I've heard people bash WinXP for ages. It's a good, solid OS, as long as you keep it tuned up.
I've had the unfortunate need to replace two motherboards in the last three years, both due to bad capicitors. One directly, one indirectly.
Every time you replace a motherboard you need to do a repair install of WinXP. If you have a non-OEM copy of WinXP you can call MS to reactivate WinXP, no problems. If you have an OEM copy and your hardware hasn't changed, no problem.
To do a repair install of WinXP, first, make a bootable WinXP with SP2 slipstreamed in. Google it, you'll find out how to do it. Boot off of the CD. If you have any funky hardware that WinXP doesn't recognize, press F6 to specify hardware during install. You will eventually get to a screen that lets you choose between the Recovery Console _R_ or regular setup (I think it's enter for that). Do a regular setup. You will eventually get to a screen that tells you it has found an already installed OS and it asks if you want to Repair _R_. Select Repair, and it will erase all your hardware data and delete all the MS-supplied files but keep everything else intact. It will then merge the existing registry information, including user information, into the new install. Think of it as a spring cleaning.
I have done this every year or year and a half, and I'm on the same basic XP install that I loaded in February of 2002. Keep in mind I don't use my PC for a lot other than websurfing, email, managing the XBOX, etc., but I used to be an avid PC gamer. That changed once I got my XBOX and my 50" Sony HD set :)