|Try removing and reseating memory and all connectors.|
Remove memory and see if you get the same beep tone, if you do, replace the memory.
You may be able to test some components in another machine, like adding the hard drive as a second drive on it and see if you have some access to it there.
Next time it is time to clean, get a can of Dust Off or similar and blow the dust out.
You have to be a little bit crazy to keep you from going insane.