I usually recommend repairing a computer if 1) The cost is less than half that of a comparable replacement 2) If I think that the unit will last for two or more years.
Your data can usually be salvaged even from a computer that is beyond repair. It can then be transferred to a new PC, the web, or an external drive. If you decide its time for a new PC/Laptop consider repairing and/or recycling your old unit by passing it along to a friend, family member, or charity - Please don't abandon it in a closet or throw it away!
-Michael