I had a friend give me a computer with Windows XP on it. However, the computer did not come with an XP license, and I don't seem to be able to reinstall Windows through the key that's on the computer.

I ended up replacing the motherboard and processor, but now it won't load windows properly. This is presumably because the current installation of XP does not have the proper drivers installed to run the new hardware. If I tried to run Windows Recovery/Repair, aside from being told that the CD I have doesn't have all the necessary files, it would prompt me for a license key that doesn't work.

I'd like to know if there's something out there which installs necessary drivers in the same fashion as the XP installation CD does, only without attempting to install XP or asking for license keys. It also needs to be bootable, since I can't get into Windows at the moment. Anyone know if anything?
If you know the license key and the version of Windows XP it was originally from, all you have to do is find a matching copy. So if the key was from a Windows XP Pro Service Pack 1 CD, you just need to find one that matches.

Besides that, don't know what to tell you. Generally, changing out the mobo and processor is enough to kill Windows as that is like replacing 70% of the computer. Chances are you are out of luck on that install.

You should, however, try rebooting into safemode, as this often works even after major hardware changes. Once in safemode you can probably uninstall a lot of drivers, and install new ones. To get into safemode, press F8 during the transition between bios and OS
In response to Danial.Beta
You don't happen to know of any way to install drivers on an XP operating system that currently isn't in use, such as one that's installed on a secondary hard drive, do you?

If I took the hard drive from that computer, put it in a computer that was running properly, and could install the necessary drivers on the dysfunctional OS, that might fix the problems.

I just had another computer with a version of XP that I couldn't reinstall burn out today. I wish I could transfer that hard drive to another computer and run that XP from there as well...
In response to Foomer
I do not know a good way. It might be possible to put some driver .inf files in the right spot, but if you can't even get into safe mode, chances are there is some nt kernel level configuration that is the issue, and no amount of drivers will help that.