I bought a really nice AMD 64 X2 4400+ Dual Core over 6 months ago. We all need one, but then if we don't have 64 bit software...
It's locked up about 5 times since I bought it. The subsequent reboots take about 10 minutes to get the login screen. So basically every reboot is that long and the hard drive thrashes to do even the simplest tasks. I spend many long nights trying to figure it out. I did many things like run MSConfig for logging driver loading to analyze, defragmented the drive for a whole day because the drive was slow, run a before and after registry file diff, and searched the internet until 3am for several nights in a row. The "quick" fix was to reinstall the operating system and all my development and database software because I wanted to use the computer before it becomes obsolete. Tonight it paid off.
I think this may happen more to people as time goes on. Several times the lockup and reverting to slowness occurred while I was remote connected to this computer. The root problem is that the Windows operating system will step down the Hard Drive and CD drive speed if it gets CRC or timeout errors. It then converts it from DMA to PIO Mode. There might be improvements in XP SP2. So in case anyone else encounters this, here's the answer:
http://support.microsoft.com/kb/817472/
There are a few others who explain this well:
http://users.bigpond.net.au/ninjaduck/itserviceduck/udma_fix/#Disclaimer
http://www.michna.com/kb/WxDMA.htm
Hopefully helping others,
-Vince