I've read all the posts here with interest as I've been posting a similar woe on the Hard drive forum. My problems started as most of yours have, but now I can't copy files from one HDD to another without having a freeze within 30 secs of starting the copy. Problem also exists when running in Safe Mode.
My system is:
Abit KA7 mobo (latest available Bios; now set on fail-safe settings ) - K133 chipset running Windows chipset driver as advised by Via.
AMD K7 750 CPU running at normal clock speed on fsb of 100Mhz( Temp = 34C. Mobo/case temp = 27/24C)
1024 Mb Crucial PC133 Ram running at 133 Mhz and 10nanosecs bios timing ( down from Normal whilst fault finding)
Promise ATA100 Controller running 1 x ATA100 60Gb drive and 1 x ATA66 20Gb drive
DVD drive on Primary IDE
CD-RW drive on Secondary IDE
Matrox G400 Video Card with Matrox tweak to be compatible with 4xAGP
Hercules Sound Card
Win2K (SP2) and all latest updates & security patches
Wacom Tablet
Smartcard reader
Umax 5450 Scanner
Above 3 running off a powered USB hub
HP DJ990Cxi running off its own USB port
Firecard, but nothing connected to it.
Elsa 56K PCI modem
Now I have 9 devices all using IRQ 11 !!
I'm also tearing my hair out trying to fix this problem as I can't do a Win2K re-install without first copying some important files from the O/S drive to the second drive.
Seeing all the advice in this thread, looks like I'm for some heavy oiling of the midnight burn.
Cheers Guys

)
PS the answer never was given on how to re-allocate IRQs :-(