Pros: In Windows XP Administrative rights truly means full access, no UAC, not demanding on resources.
Cons: Flat user interface, less media features modern Windows OS, outdated.
I've used many operating systems in my days. I used to be a real-time operating system kind of guy and also more into UNIX (that's not Eunuchs). However, because of my current job I've become more of a Windows user both as a Professional and as a consumer. I own and I am using Windows XP Professional SP2+SP3, Windows XP Media Edition SP3, Windows Vista Home Premium, Windows Vista Business Edition, and Windows 7 Home Premium, and in the past I've used dozens of Windows OS versions/editions.
Windows 7 (Home Premium) is probably currently my favorite Windows OS for home use because of all the media capabilities, the slick interface, and the fact that it seems to be relatively stable. However, Windows XP Professional is also one of my favorites but for different reasons. We have to use Windows XP Professional at work because Windows Vista and Windows 7 are incompatible with specialty software we use as well as some legacy hardware. Windows XP Professional is outdated and it has its weaknesses but it also has its advantages. I should say many of its weaknesses were addressed with Service Pack 2 and Service Pack 3.
I should add that when I was at Best-Buy the other day to buy a computer for a friend they repeatedly asked me if I wanted to buy an XP machine despite the fact that I never asked for that. I was surprised to hear they are still pushing XP.
Windows XP Descends from Heaven to save the DLL user from DLL Hell
After surviving horrific Windows operating systems like Windows 3.1, Windows 95 (blue screen of the day), Windows 98 (blue screen of death the sequel), Windows NT, especially Windows NT 4.0 came to the rescue. In addition NTFS arrived and saved me from the oddities and restrictions of FAT32. Then came a few slow years with Windows 2000 and ME, and then came Windows XP, the first consumer oriented operating system based on Windows NT. Like Windows NT it was quite stable and it also solved the problem with "DLL hell". The DLL (Dynamic Link Library) Hell arose from different versions of the same DLL (same name) being used, or different versions of the DLL's being overwritten. This could lead to lots of strange effects like the installation of a new program breaking other existing programs. I used and also created hundreds of Dynamic Link Libraries in my days, so I had to deal with this a lot. Different aspects of DLL Hell were solved gradually but Windows XP took one big step forward in ameliorating DLL Hell via its side-by-side assembly solution.
Other improvements in Windows XP over previous versions was, for example, a nicer and more intuitive user interface, better device support, and support for modern image file formats (Windows Picture Viewer). Windows Explorer improved a lot in Windows XP. One new feature that I liked was the "My Networks Places" wizard, which made it easy to add remote network places to your "My Windows Places". For example, to connect to the godaddy's servers via ftp just start the wizard ("Add a Network Place") and fill out the server name and a password if needed, and now the remote server directories acts like one of your own folders.
Windows XP was such an improvement that nothing new seemed necessary to many people for many years, and so the years passed and Windows XP stayed around.
Windows XP Professional
Windows XP comes in the following editions;
Windows XP Home edition
Windows XP Professional
Windows XP Media Center Edition
Windows XP 64 bit edition 2002 and 2003
Windows XP Professional 64 bit edition
Windows XP Special market editions
As mentioned, at home I have the Windows XP Media Center Edition and the Windows XP Professional edition, and recently had the Windows XP Home edition. At work I have the Windows XP Professional edition by necessity.
Unlike the Windows XP Home Edition the Professional edition supports Windows Server domains. This is an absolute necessity for a work place, where you need domains for large network management. In addition Windows XP Professional also supports the use of two processors (our laptops), remote desktop server (control PC remotely over LAN), and it has IIS, which is useful if you want to create and test active web pages/sites on your PC. These features are all absolutely necessary for my work place. The system requirements for the Windows XP Professional edition (as well as the Home Edition) are fairly modest, 64MB or better 128MB RAM, hard-disk space 1.5GB, and a 233MHZ processor or better.
Overview of Windows XP with SP3 (32 bit)
It took us a while before we upgraded to Service Pack 3 at my work because Service Pack 3 conflicted with our security authentication at the time. Now we have upgraded and I upgraded one of my XP machines at home as well. If your computer is configured for "Automatic Updates" you probably have had the Service Pack 3 already automatically pushed on you. Many people have "Automatic Updates" turned off because it can be a quite annoying feature. If not you can get a CD or download it for free if you have Windows XP SP1 or Windows XP Sp2 already. The download and the installation will take quite some time (several hours), so you should be ready for it when you do it.
Service Pack 3 was released in April 21 2008, almost seven years after Windows XP was first released. It contains thousands of fixes and updates, many of them addressing security issues, as well as new features, including the Windows Imaging Component, MSXML, Microsoft Management Console 3.0, a WPA2 update, group policy support for IEEE 802.1X authentication for wired network adapters, it turns out black hole router detection by default, etc. Basically, unless you have a problem with an aspect of SP3 (for a home computer that is very unlikely) you will get a better and more secure Windows XP with SP3, and I therefore recommend that you upgrade.
Comparing Windows XP SP3 and more recent Windows OS, especially Windows 7
Windows XP definitely have some weaknesses in comparison to more modern Windows operating systems (for example, Windows Vista and Windows 7). First, the common 32-bit versions of XP have a quite limited address space compared to the 64-bit versions (the 64-bit versions of Vista and Windows 7 are quite common). Unless you edit the boot.ini file Windows XP 32-bit only supports 2GB of memory. If you edit the boot.ini file (as I've done) you get 3GB, the theoretical limit is 4GB. 64-bit Windows OS is typically higher, 8GB, 16GB, 128GB, or 192GB. I should say that the same is true for the 64-bit version of XP, which has memory limit of 128GB, but that is not what I have or is reviewing.
The Windows XP user interface does not have the 3D feel Windows Vista and Windows 7 has and XP does not have Aero Peek, the nifty pop-up thumbnail previews of your windows, or Aero Shake and Aero Snap. On the other hand many people find those new features distracting so it is also a matter of taste. XP does not have the new Media capabilities of Windows Vista and Windows 7. On the other hand the Windows Photo Gallery in Windows Vista was worthless and the more useful Windows Live Photo Gallery and Windows Live Movie Maker are downloadable to Windows XP as well (SP2 and above).
As far as stability goes Windows XP SP3 appears to me quite stable. I have had the rare occasional stop error but that is also true for Windows 7. For Windows Vista stop errors seem to happen more often than for both XP and Windows 7. So in that regard I think it is a wash. The same is true for speed. Windows XP appear to boot up quicker but it is mostly a wash with respect to running applications.
Some people find the UAC (User Access Control) in Windows Vista and Windows 7 problematic and the UAC has given me some significant problems even in Windows 7 (despite full administrative rights). Even though the UAC is a security feature some might say that XP is better for not having it. Another probably related and annoying Windows 7 feature is that it will not give you full access rights to some operations even if you are logged in as an Administrator. You have to explicitly change this and in some cases I found this to be tricky. The latter is something that has greatly annoyed me.
I should also add that I have had some strange problems with Windows Vista and Windows 7 that I have never seen on Windows XP. Sometimes my wireless printers go bonkers when there is a print error and I am connected to a Vista machine or a Windows 7 machine. I cannot cancel print jobs, and I cannot even delete and add the printer back. I'll get "Operation could not be completed (error 0x00000709). Restarting the computer is the only thing that helps. I've never had this happen to me on an XP machine.
Another thing that annoys me is that the new Windows Explorer (in Windows Vista and Windows 7) does not display the pixel size of an image unless you select it, which lowers my productivity in certain areas. There are also 100's of XP features that many people have gotten used to that were removed in Windows 7. I finally the newer operating systems require more resources. For example, Windows XP Home Edition and Professional require 64MB or realistically 128MB RAM while the Windows 7 32-bit edition requires 1GB and the 64-bit edition 2GB RAM. The same numbers for hard disk requirements are 1.5GB versus 16/20GB.
The previous section makes it sound like I am praising Windows XP as the best Windows operating system. Well, I am not. I like Windows 7 better than Windows XP for a number of reasons including the new Media features, the nicer user interface, etc. However, Windows XP is still a strong contender despite being so outdated. Considering that some people cannot upgrade to Windows 7 because of specialty software or legacy hardware I can see Windows XP staying around for a little longer.
A minor note: You could also set up a dual boot system and use both Windows XP and Windows 7 but then you need to partition the hard drive and install Windows XP on the C partition (I have not done this).
In any case, Windows XP was a big improvement over its predecessors and it is still ticking. If you have Windows XP and you don't use specialty security software that might conflict with SP3 then you should upgrade to SP3. If you need to connect to a domain, well then you need Windows XP Professional.
Other than that all I can say is; think through whether you need/want to upgrade. Both Windows 7 and Windows XP are good operating systems.