Dell XPS 410 Wont Boot

I have a Dell XPS 410 for over a year now and recentlly the fan started making a weird noise then it went away and the next morning the comp was off adn wouldnt turn on then a few days later it turns on then a day later wont turn on again and now 2 weeks later still wont turn on .  I removed all the parts that connect to the power supply and was able to get it to turn on and when i would put the 2nd memory card in it would turn off and restart adn turn off and restart and then not turn on.  so i replace the memory thining it woudl work but dosena dn now it still wont turn on.  I took the PSU to best buy and they said its fine.  I dont see how it could be the mother board when its just over ayear of having it.   O and the AMber light on the hard drive is on.   Any suggestions  ???