do you have the box your computer came in?
Yes? Good. Box it up and send it back.
j/k
You likely have a software problem. Software problems do not mean your computer is broken. Software is like the writing on a chalkboard. When it has problems, it's like the writing on that chalkboard gets smudged or messed up. You do not need to replace the chalkboard to resolve the problem.
What brand is the computer? Call the OEM and see what kind of assistance they can be.
You might see if you can run a scandisk or defragment your harddrive. Hit F1 with no programs running, and you'll get the HELP window. If you type in SCANDISK or DEFRAG, it will give you directions on how to do those two things.
Also, do you have antivirus software installed? Did you install any programs right before this started happening?
Run a virus scan on your computer, after checking to see if there are any virus definition updates from the AV software's publisher. Go to the Control Panel and open Add/Remove Programs. REMOVE any programs you do not USE.