I have the USB version of this compact flash card reader on two w98se machines (with USB on the motherboard) and I previously had one on a w95 machine with USB on an add-in pci card. Plugged it in while the pc was on, windows detected it, loaded the drivers from the cd and rebooted. Windows assigns a new drive letter to the reader. I've rebuilt these same machines a few times, and never had a problem with this reader. On one of these machines I've also got a nikon camera serial adapter, scsi (with 2 devices), video capture pci card, extra ide ports on a pci card, a sound card, a printer, and drivers loaded for a couple other USB devices - sharing IRQs all over the place and nothing ever conflicted with the san disk reader.
If you've got USB enabled, haven't used up all 24 drive letters, and your cf reader doesn't have a paper clip stuck inside shorting out the contacts, then I'd guess the problem is not the reader. (not much help, I admit) Jim