Windows XP was a good OS; problem is, it no longer is. It has gotten so bloated with all the SPs and updates that it's surprising it still runs efficiently, sort of. (What is bewildering is that people keep asking for it.)
I had to upgrade to Vista in order to network with my recently acquired laptop which had Vista Basic on it. XP would just not see the laptop. The lappy would see my XP workstation just fine, but the latter would just refuse to network with the former. So, I shelled out the cash for an OEM copy of Vista Home Premium 32-bit. The network problems went away and I used Vista for about a year. The workstation stays on 24/7 and I seldom have to reboot. Vista was stable as a rock and smooth as a baby's butt. PS CS4, Painter 11, Office, even games that were not supposed to run well in Vista performed like champs. Never a problem. And I didn't even do the automatic updates. It was months before I would install an update or service pack. Vista just worked fine.
Then, wanting to use two extra sticks of RAM that I had laying around, and seeing how CS5 is now all 64-bit apps, I decided to upgrade to a 64-bit OS. I could still have gotten a 64-bit version of Vista, but with Windows 7 already out and getting good reviews and all the hype, I purchased an OEM copy of Windows 7 Business 64-bit. Biiig mistake, if I have to paraphrase that Arnold Schwarzenegger character.
First thing: there goes my network. Now the Vista laptop would not access the W7 workstation. Little wonder, since M$ changes the networking in every new version of its OSes; tactic that they use to force people to upgrade. Sure, they say Homegroups makes networking way easier to set up and use, and it's the greatest thing since the invention of ethernet, but Homegroups works only with machines running Windows 7. A-ha!
Worse problem than networking woes was the fact that W7 performed like a snail on crutches. Applications that in Vista took seconds to open, in W7 took over half a minute. All Adobe apps opened way slower. Office apps took almost a minute to open (although the problem there was AVG, which was scanning files prior to opening them, so uninstalling AVG and putting on MSE took care of that), and a Recycle Bin that takes about 30 seconds to open its window. Overall, Windows 7 was slower than Vista. Sure, sure, it starts faster than any other M$ OS! But for someone who never shuts down his machine or puts it into hibernation/sleep, what good do faster boots do? I want my apps to run fast, not the boot process.
I was driven nuts and ran for the Mac shop.