depending on the age of the pc some pc use cd to restore the factory image and some pc vendors switch over to putting the restore image on the hard drive. if your pc has the image on the hard drive then there should be a f key you hit at power up to start the restore or it may be in the bios. if it a set of cd then put the cd in that says factory restore or windows restore and set the cmos to boot from cd first. it start the restore on the next boot. a word of warning if you do that you lose all the data on the hard drive. on your issue try downloading and make a hirem boot cd. run anti virus scan see if it a virus. if your hard drive is clean run hdtune and hard drive vendor test tool to see if your hard drive is healthy.