if you're running windowsxp, then there's already backup software on it, and you can use the task schedule program to run that with.
start>all programs>accessories>system tools>backup
also
that has a lot of options for free backup software,
I use linux mainly, and backup using a cron job. there's not a lot of stuff on my windows machine that I would need in case of a system failure, so sorry I can't help you out more.