Hello all, I'm hoping one of you might know what's going on with my new system. I just installed a new motherboard, ram, cpu, cooler, and hard drive. This GIGABYTE GA-MA790XT-UD4P is my motherboard with a Phenom 2 720 BE. I hooked up my old ide drive complete with operating system and surprisingly it booted up. I tried it just to see if it would for some quick benchmarking. After doing that I went ahead and inserted the xp disk. Installed it on the new sata drive. After the install I then had the choice of which operating system/hard drive to boot off of. So then I removed the ide drive and tried to boot off the new sata drive. The motherboard said that there is no bootable disk... So I double checked bios to make sure it still sees the hard drive. Which it does. It's also set to boot from the hard drive first. So this is a comlete mystery to me. I went ahead and plugged the ide drive back in and now the motherboard sees both again. lol.
although i might be WAY off, i think the reason it wont boot from the second drive without the first one installed is that the bootloader(i believe its called a bootloader) is on the first drive. So as Zip said, uninstall the IDE drive , leave only the sata drive installed and do a fresh install of the OS.