MacBook not charging I have a 2008 Black MacBook. The battery indicator says 'Not Charging' and if I remove the power adapter it powers off instantly. 

I had OS X installed, installed Windows (Not bootcamp, Windows only) and then reistalled 10.6.8. Since reinstalling OS X the battery has never charged.

The battery only has 68 charge cycles on it, so it seems strange it would have already died.
As suggested, SMC reset should be your first port of call.

If that doesn't change anything, try removing the battery and see if the system recognises the change. (Status should change to "no battery"/battery icon with an x). If it changes, that pretty much means that the battery is toast.

I'm guessing that your battery has failed as this is the most likely cause of these symptoms. Cycle counts aren't a sure fire way of determining battery health, they can just die.

If your battery is less than 12 months old, you are entitled to a replacement from Apple.