Windows Keeps crashing after boot

My math teacher gave me an old Windows XP computer a few years back and last year, There was a power surge in my home and the motherboard was just completely fried. I took the hard drive out. Today, I found a different computer and put my hard disk in that. It booted up fine until it got to the login screen. Then, It gave me a bsod with the code 0x0000007E. I went to safe mode with networking to download an error fix. Then, when I go hit login, it tells me that I need to activate windows outside of safe mode.

Can anyone tell me what to do?

edit: I have gotten into safe mode, found my product key and verified that it works. I just need to know how to activate it from within windows recovery console. Then, I can logon to safe mode with networking, install a blue screen fixer and reboot.

can anyone tell me how to activate it?

the blue screen is caused, because you're taking a windows drive, and putting it into a completely different PC to use. This is generally not recommended. It's better to completely reinstall windows. This should remove the blue screen.

This will allow you to login properly, and if your windows install is not tied to an OEM (OEM install means it was preinstalled on the old computer) then you should be able to call the number it gives you during activation, and switch the license to your new computer.

If it is an OEM install, you cannot use that install on any hardware other than the computer it came with.