Windows loads on friend's machine, not mine

I have 2 hard drives, one for the OS and program files, and one for everything else. I decided to reformat/reinstall windows on my master drive, the OS one. I took it out of my machine, plugged it into my friend's, and installed windows xp pro on it. Then I rebooted and his computer recognized it right away and I had no problems booting up windows on his machine. So I move the harddrive to my machine, plug it in as the master, even take out my other drive, and when I boot it up, I get a message similar to:

Please select correct device or
insert bootable media

It just won't load windows. I thought it might be the bios so I went in and reset all the defaults, then even put the hard drive in front of the floppy in boot order.

What's going on... I'm working on a job from home and I need this working ASAP. Help would be highly appreciated.

I got it using boot disks.

are you using the exact same motherboard and cpu?

Glad you got it to work. In general, you cannot move hardrives around between computers and expect them to boot. There are too many variables and hardware dependancies. If you have the exact same setup it might work, else you'll have to use boot disks (like you did) or try to repair the install with the cd.