to back up your registry go to start,
run,
type regedit, that opens the registry editor,
go to file,
then click on export,
select where you want to save your registry,
make sure that at the bottom under "Export Range" select "All" instead of "Selected branch"
click save, and that's how you make a back up of your registry
Good luck,
and have patience, some will come and explain your other question