you shouldnt have to back up anything
with drives are cheap nowadays,
buy 2 drives:
1 about 20gb, install your OS (winXX, or what ever favour), install all your programs (Office, CD burning, CD ripping etc, anti virus). Test it make sure it works ok for the purpose. Ghost the whole drive into your second drive (drive could be any size you like), burn the image onto CD (best if you can make CD bootable).
Any problem with your C drive or its programs or been nuked by virus, just ghost from the image and presto, you have good drive again
As to your second drive, save your data, your works your download into seperate folders, when it get to 650 or 700 or 4.7GB if you are rich enough to own DVD burner, just burn to CD or DVD.
If you install and deinstall software frequently, it would help a lot because your working C drive will be "intact" forever
If you like something you've installed and want to use it regularly you just have to ghost your C drive again, and burn another image, (a full XP and SP1 install + Office and other progs comes to about 4gb, ghost with high compression, i squeze it into 3 CDs)
Ghost 2001 wont do XP with NTFS but it will do XP with FAT, Ghost 2002 and 2003 does it but it needs serial everytime you un pack it, very inconvenient)