I couldn't find a BIOS category so I figured this forum was the closest fit with my problem. In a nutshell, my Dell Dimension 4100 BIOS is claiming my drive that has been working without incident for a year is suddenly "not installed." I've been using a Dell Dimension 4100 P3 1 GHz for a couple of years without problems. One of my other computers randomly decided to stop working (another story altogether), so I used the Dell to do analysis on the drive. Since it was a SeaGate hard drive, I used SeaGate's online scanner to scan it for errors because I suspected it was faulty. I also did some virus scans. I restarted a little while later, and the Dell computer would get stuck on the Dell post screen. It wouldn't even go into BIOS after I hit DEL (it would freeze). So I flashed the BIOS (A11 from Dell's website) after reading some threads stating that maybe I had screwed up the BIOS (I was really confused as to why things were messed up). I still had the same issue where it would get permanently stuck after the memory testing on the post screen, and wouldn't let me access the BIOS. I did some more reading, and read that hardware components could be messing up the computer load process. It turns out, my CD-Rom drive was faulty or something, so when I removed it, BIOS was accessible. However, now I faced a new problem: BIOS doesn't recognize the original drive that was in the Dell, which is connected to a PCI slot via a Promise Ultra TX2 ATA controller card. So Windows won't load because my computer doesn't think there's a drive installed. The Dell tries to load PXE and other networking stuff, but of course fails. Oddly, the screen following the ATA card detection process (after post and BIOS loading), the computer lists all the IDE devices and properly identifies HDD-0 as a Maxtor 186mb drive (which it is). The Dell BIOS is pretty limited in customization. In the past, it has always successfully detected installed hardware. Under IDE Configuration, my other CD-ROM is listed (the one that isn't faulty), but under HDD-0, it says "not installed." I chose auto-detect. I tried the drive in question on another computer on the IDE motherboard slot (not through a controller card) and it is recognized just fine. I can't use this drive directly on the Dell's motherboard IDE slot because it's an old computer and I will get data corruption since the drive is larger than 137GB (I figured that issue out long ago). I updated the BIOS with the ATA controller card BIOS upgrade file from Promise's website. The jumper settings are set to Master. I've swapped IDE cables, PCI slots, and power cables. Ooops, while I was tying this, I restarted the computer after switching PCI slots for the ATA controller card, and now when I restart I get a black screen that says "Invalid Boot Diskette; Insert BOOT diskette in A:". There is no disk in the floppy drive. Could I have a BIOS virus? Does something like that exist? Could that be why the drive on the other computer failed, and then the CD-Rom drive on the Dell, and now this error? Thanks for any help and I apologize if this is rather long-winded.