^ What rhysiam said.
Additionally:
1: It's usually brownouts that destroy equipment, not spikes. (especially with a switching power supply.) OHMS Law: When the amperage goes down, the voltage goes up, and fries whatever is turned on. So a UPS is MUCH more important. Luckily, computers don't require those uber-expensive "always online" UPS types. The cheaper ones are just fine. (unless you use an internal audio card and sound quality is important.)
2: Cheap spike protector strips go bad after a few years, (the ground integrity starts to fail) at which point they cause more harm than not having one. One should test any such strips about once a year, to make sure there is a very low impedance from input to output on all three wires. (but especially the ground.)