How often you back up your data can only be determined by how important you feel it is(http://www.szukajka.boo.pl/search.php'q=Computer+Virus&aff=27193&saff=1). Answer this question,http://www.hotels.ovh.org/search.php/keyword=computers "If my hard drive crashed right now, would I be alright if I had the data from at least (time) ago?" For some people, a daily backup is required while for others it may be weekly depending on how often you create important data files.

Of course you would want everything but if you could have the data from 1 month http://www.vikivip.com/?title=computers , or 6 months ago would that be sufficient? Whatever time is sufficient, mark it on your calendar and set up a reminder on your PC to help you remember. Another idea is to use an automatic backup program where you can set up specific times for the backup program to run.