Bad capacitors are a somewhat common problem with desktop computers from 1999 – 2007. Reports of some bad caps are still coming in now late 2011. Why has this taken so long to fix you might ask? Simple We have to wait for them to fail before we know that they will need replaced. The larger issue is that they only show up bad after use over a period of time. Poor quality electrolytic capacitors test the same as good ones when new. The difference is in the liquid in the capacitor, the electrolyte, will produce hydrogen and cause the caps to bulge and fail prematurely. In computer terms this means that you computer will start acting funny with random problems and eventually die.
What can you do to avoid this? Simple bring it in to your friendly neighborhood computer repair person and let them take a look at it. Most won’t (and shouldn’t) charge to just look at the motherboard.