An oldie, but a goodie.....

This simple batch file backs up your registry to a new folder as well as 6 system files.

This batchfile also creates another batchfile
called fixit.bat, so if something happens, you can boot to MS-DOS, and simply type fixit (without the quotes) and it'll restore your registry and system files. It also puts a restore.txt file in there so you can do it manually if you're so inclined. :-)