7NJL6 won't boot from WinXP CD when HD replaced

I bought a new hard drive (Seagate Barracuda 80GB SATA), and I was planning on unhooking the old one and letting my winXP CD boot and do a fresh install on the new HD. But, once I unhooked the old one, the computer won't boot from the CD rom. (I did set it to boot from CD rom in the bios.) The processor and ram check shows up, then I get the usual options (press DEl to enter setup, press ESC for boot menu or something like that) and at this point I can enter the bios, but it doesn't react to ESC. After a few seconds, the next screen comes up saying Realtek something-something Boot agent, Press shift F10 to configure. Doesn't react to shift F10. After a few seconds it restarts and the whole thing keeps looping over and over. When it checks for IDE drives I can see that it picks up the CD rom.
So I unhooked the new HD, put back the old one, and boot-up was fine. I can boot from the CD now.
The motherboard is a chaintech 7NJL6, with Athlon XP 2900+. I've never had a problem before.
http://www.chaintechusa.com/tw/eng [...] &PISNo=277 <-- this is the motherboard
http://www.chaintechusa.com/tw/eng [...] &PISNo=277 <-- I made the driver disk but obviously never got far enough to use it.
Any suggestions?