When I install software (or drivers for new hardware) from the factory CD, usually a "setup" program takes over, copies the needed files into the directories where they belong, and makes any necessary Registry changes. Just copying the files, even into the correct directories, may not be enough if the Registry changes aren't made too.

I've found that when I download things like printer drivers or browsers, what I get is an "installer" -- typically a self-extracting .exe file -- on my Desktop. When the .exe is run it creates any needed folders, unzips the appropriate files into them, and pehaps runs an .inf file or something to update the Registry. I collect these installers in case I ever need them again (as I did when my hard drive crashed last year). I have a folder called Recovery with copies of all my drivers, installers, and my notes from when I last used them, and after any changes (like a new installer) I burn the whole thing to a CD.

For routine backups (daily, more or less) I copy any changed files from certain folders to a CF card ("Compact Flash" memory, originally meant for cameras and such). Once a month or so, I burn everything on the CF card to a CD and put the CD away in a fire chest. If there's too much data for one CD I'll do it in two installments -- perhaps all pictures on one CD, everything else on the other. Of course saved data from 2 years ago is worth a lot less than the stuff from yesterday so when I run low on fire chest space, the oldest backups are the first to get relegated to the closet shelf.

Btw, I don't try to make backups of Windows itself nor most of the files that Windows maintains. I figure if Windows ever gets so damaged that I have to replace system files, I'll be better off starting fresh with the installation CD.