BIOS does not recognise the DVDCD drive

Appoloies for the length of this post.

Having researched all day, I've been unable to find an answer that works, so I'd like to ask why would my BIOS suddenly stopped recognising my DVD-CD drive.

My new system build, uses new components except for the 40 gig hard drive which was previously installed and working with an operating system in another PC. In my new system, I've used a 350 watt power supply in an Asus tower, an Asus K8V-MX motherboard a Sempron 2600 processor with 512 meg of DDR RAM. Setting the BIOS boot sequence so that the DVD-CD drive was first, I've parbreastioned and formatted using an XP pro disc, which went to within 20 minutes of completing the operating system installation. At this point it stopped and displayed a blue screen specifying that several files were missing and windows had shut down to protect my system. Several attempts at reinstalling, brought up a similar message.

Suspecting a possible conflict, I tried installing Windows 98 and used a Windows 98 startup floppy disc to FDISK and format the hard drive. After the parbreastion and format, Windows 98 installed and worked normally on the 40 gig old drive. I then tried upgrading from Windows 98 to XP using the XP disc and once again it stopped at around 30 minutes from completion, having found more missing files. I then attempted to install this XP disc on another machine and it installed normally.

Since my failed attempt at upgrading from 98 to XP, I have re-tried several times using the XP disc and also trying with the 98 CD, using FDISK and format. When using the 98 disc, I can see that DOS drivers are being loaded successfully for the CD drive in the DOS sequence and I manage to successfully parbreastion and format the hard drive. I can also select the DVD-CD drive as my first boot in the BIOS, but when I reboot with an operating system disc in the drive, I get a message saying that the wrong boot disc is installed and to reinstall the boot disc and press enter. No matter what I select in the BIOS as first boot device it reverts to the floppy.

I've updated the BIOS with the latest file using EZ flash from Asus and now, when I re-boot, with the DVD-CD set as first boot device, I get a C: prompt but cannot access the D drive from it and when I try, I get an "invalid drive" message and again told to reinstall the boot disc and press enter. The floppy can be accessed from the C: prompt but this only allows me to access the FDisk-format cycle again. I'm now at a loss as to how to access the DVD-CD drive to install the operating system, can you help please.