Software :: Can't Boot From CD Drive?

My wife's desktop computer is running Ubuntu 10.4, with no problems after the recent upgrade, on a single 640GB HD. I decided to add a new 320GB HD with a clean install of Windows XP. I thought I could then reinstall Grub, either by booting the original Linux system on the original HD or using a live CD, and evolve her computer into a dual boot arrangement. I use a dual boot system on my own computer, but I did it the easy way: I did a clean install of WinXP on a new HD, got it running, and then did a clean install of Ubuntu on a second HD. Grub found its way around and everything went smoothly.

Now I had the opposite and less desirable situation of an already installed Ubuntu system and wanting to add and integrate a new Windows install. I formatted the entire new HD as NTFS, using gparted under Ubuntu. I then tried to install WinXP from the MS CD. I changed the boot sequence in BIOS. When I booted, the system completely ignored the CD drive and went directly to the HDs to try to boot!

Problem: The computer insists on booting the HDs; it ignores the BIOS setting. Therefore, I can't boot from the CD drive and install WinXP. Here are some further symptoms: 1.) I get a Grub prompt: "grub restore>". So I tried the MS WinXP disc in my own computer. With a BIOS change, it booted into the WinXP setup program, as expected, direct from the CD. My conclusion: the WinXP installation disc is OK.

2.) I disconnected the new HD and rebooted. I was still able to boot into the original Linux system, but the CD drive was still ignored.

4.) I reconnected the new HD and DISCONNECTED the Linux drive. Rebooted. The system still ignored the CD drive, went for the HD, and ended up with an error command line prompt: "grub restore>". With my Linux system completely disconnected and a freshly partitioned HD installed, where was this Grub prompt coming from???

5.) So I disconnected BOTH drives (i.e., NO HDs installed!). Then the system booted up the WinXP CD and windows setup. But, of course, I didn't have any HD installed. When I reboot after re-connecting the new HD, the system once again ignores the CD drive and I get the Grub restore prompt. Conclusion: the CD/DVD drive is working OK.

QUESTION: Does Grub write something to the BIOS/CMOS? I didn't think it did. But then, why do I keep getting this bizarre grub prompt when the only things installed are a clean NTFS-partitioned HD and a WinXP disc in the CD drive?

As always, I hope I'm not asking for something that should be obvious. I should add that most of these boot attempts were after changing ALL three boot devices (boot priority/sequence) to the CD/DVD drive in the BIOS. Still no luck.