Boot problems

hiya guys just installed ubuntu onto my desktop that was running windows xp. I needed to run mysql and php programs so i thought this would be the best idea. now i cant boot into either of them, just tried disconnecting the hdd with ubuntu installed on it and its still the same, i also set the bios to boot from hard drive and nothing else but it is still looking for a cd when i boot??????? really gettin on my nerves now, and also how can i choose which os i want to boot into when i turn the computer on cheers!!

I have run into that before, perhaps in a different way. I have two hard drives, one for Windows, one for Ubuntu. I can disconnect the Ubuntu drive but still it will look for Grub and menu.lst upon booting up. That has made me wonder where that information is stored...in the CMOS? On the Windows drive as well? That will be something I'll have to look up further.