Weird boot issues

I've just put together my new computer, and I installed Windows 7 Ultimate x64 on to my Samsung 1Tb hard drive. I wanted to copy over some files from my old 40Gb hard drive which had Windows XP installed, so it was plugged in at the time.

Windows 7 definitely installed to the new hard drive, and my computer ran fine for a while. I was unable to copy files from my old hard drive to due permissions issues (but that's another story altogether), so I unplugged it.

When I turn on my computer with it unplugged, it's now unable to boot. In the BIOS I've checked that the Samsung is the primary boot device, but it still won't boot. My motherboard (Asus P7P55D-E) just gives me a message about rebooting with a proper drive connected. It's as if the file which tells the BIOS Windows 7 is installed is stored on the old hard drive.

Is there any way I can repair Windows 7 on the Samsung drive without reinstalling it, so that it can work without the old 40Gb hard drive?

Ah yes that's what its called, perhaps there is a feature on the Windows Installation DVD to fix it?

EDIT:

Just found this http://www.heiser.net/posts/3256

I think it's because rather than creating it's own boot loader it overwrites the XP one. I'll try ths and see how it goes.