Does your system seem to be lacking the performance it used to have, particularly with respect to disk access? If so, it could well be caused by a bug in microsoft's IDE disk handler "atapi.sys". This applies to Win2k, XP and Server 2003.
Depending on your configuration, your system should by default detect the best performance for your hard disc drives. For cd and dvd drives you may have to tell the system to use dma mode if it is available, but after that you would expect it to maintain the best possible configuration.
Unfortunately, this is not the case. If the system detects 6 timeout or crc errors on a drive, it will drop the performance to the next lower level. So if you have an ata100 drive, the level will be dropped from udma 5 to udma 4. Get another 6 and it will drop another level. But since the only displayed performance is ultra dma, it is difficult to find out that this has happened.
Worse still, there is no proper mechanism to restore the performance.
I found that my hdd was running in PIO mode instead of udma5, as you can imagine, the performance was terrible, but had the level only dropped to udma2 I would not have known. It turns out that there had probably been some i/o errors while I was testing the overclocking properties, so the system had done what I described above, and I could find no way to change it back.
Microsoft have a fix for this problem, but at the moment it is only available if you pay for a support call.
Fortunately, there is a work-around. If you uninstall the drivers for the controller (you have to remove the whole controller, not just the offending channel), then reboot, the controller is reconfigured and set back to the defaults for your drive. But note that you may have to set "dma mode if available" for your cd/dvd drives.
NOTE - using the "upgrade drivers" option does not correct this problem.