I wen't nuts trying to fix this. I had the same problem. Won't dectect the card, card won't start error 10, etc, etc, etc, tried everything I found on the forums, nothing worked. If one more person told me to switch slots I was going to go mad. I thought I had a dead card.
I found a post that suggested the contact pins on the PCI card can oxidize and not connect properly. They instructed me to take a soft eraser and rub the contacts clean. I gave it a good rub, and guess what... no more problems. Card detected properly both in BIOS and Windows. Installed the driver from the CD, it found the card, no more issues.
Try it. Let me know if it works for you.