If 1000 monkeys worked for 1000 years, they still couldn't figure out this computer issue. :/

 I´ve seen computers that were more dust than computer but they had no problem running... I highly doubt that dust is your problem...

 Are you calling me a monkey ??? Because if you are I will have to throw my crap at you :)

@ Fazz, yes I'm sure I have a cheap power supply, it's only a 300 watt that I got with my super cheap e-machine which I upgraded.

What's the rest of your system specs again?

Yeah but you know the mainboard is getting power since the fan is on... if you don´t have any powerhungry graphic cards or anything simmilar I think 300 watts should be just fine...

1.8GHz 3100+ sempron socket 754
Had 756mb of ram upgraded to 2gb
300watt power supply
Cheap mobo, looks like this:

What do you guys think, should I keep it and live with it or just get a new one?

My PC will do funny stuff on me from time to time as well, eather the motherboard has a tick or my CPU is slowly kicking the bucket... but I always ride the horse till its dead... if your PC still does what it has to do keep it... if it doesn´t do what you need it for or just pisses you off to much get a new one...

It's the eMachines T3101 it seems. It's supposed to support the 2GB of RAM. Weird problem, I'd put my blame on the power supply. You don't have another supply to test?

If you have the money you can build a new one. I'd do that.