computer woes.

My machine has been driving me crazy lately keeps crashing ,freezing etc.I've run anti virus,adaware,datbase scans etc.Its gotten so bad Ive tried repairing XP from the disk.I called Dell they are going to send me a new version of XP and talk me through the reinstall over the phone.Heres something else i thought i would pass on .I checked my tower since i keep it on a small platform on the floor.the intakes for the fan etc were COVERED in dust.took a vacum to it then opened her up and used a whole can of compressed air actually 2 1/2 cans because they would get cold.lol.Then i rerouted the jungle that was the power and other cords down there.The dusting helped but the install should go down tonight.anyone know how to back up all yout files?I got disks but they are for writing CD's im thinking it may take a ton of em to do that any suggestions?I dont want to lose all my phtos ,music stored docs etc