I saw your thread regarding making a backup:
http://forums.techguy.org/general-se...-up-files.html and decided to answer here since it is related. The answer is yes, your backup could possibly contain malware.
I suggest
before you make a backup, you want to be sure the files you want to save are clean. Download AVG8 Free Edition:
http://free.avg.com/download?prd=afe and have it do a full scan. Then backup the files you want to keep to a CD (being careful none of those files have dll, exe, com, vbs, scr or reg extensions unless you are sure they are safe).
After you reinstall your OS, install AVG8 again before you even think about connecting the computer to the Internet. Then restore you backed up files last.