GRUB appears out of nowhere after installation. HELP!!

[Jemilio3]

So here's the problem:

I was installing linux on my friend's really old desktop pc, and his desktop wouldn't boot from a cd. So I took out his hard drive, put it in a hard drive enclosure, and plugged it into his brand new Windows 7 laptop which he loves dearly. I went through the installation, took lots of caution to make sure I had the right disk, and everything went fine. (the ancient pc wouldn't boot because it couldn't find the sfs file, but I that's the least of my problems.) So I pulled the hard drive out and rebooted his Windows 7 laptop. And to my horror, instead of booting windows, it said something like:

GRUB loading..... section 1.5

Error 21

I was in such a state of shock that I forgot to write down exactly what it said. But anyway, he is really upset now, not at me because I worked on fixing it for hours and hours, but I gotta get this fixed. Anyone have any idea what happened here?

[Lazydog]

Use Windows7 recovery disk to repair MBR. You installed grub in the MRB of the windows drive not the linux drive.

[luolimao]

Use Windows7 recovery disk to repair MBR. You installed grub in the MRB of the windows drive not the linux drive.

He's right; you installed Linux on the old desktop PC's drive, but you installed GRUB on the Windows 7 machine; you have to configure GRUB so that it installs itself on the Linux drive. So use a win7 recovery disk (or, better yet, copy his data OFF the drive and then reinstall win7 if you/your friend has a retail copy) to get back the master boot record (MBR)