Question : Problem: Dell Dimension will not power up

I am having trouble getting my Dell Dimension 2400 to power up.  I have read several other questions/answers with similar issues, but am not sure that any of them are exactly like my situation.  When I try to power up the machine, the power LED blinks green.  There is no POST and the back panel diagnostic LEDs show nothing (all four lights are dark).  I have removed all power connectors and cables from the motherboard (except the power supply) and get the same result.  After much reading on similar problems the only conclusion I can come to is that the motherboard is fried.  I am prepared to buy a replacement if need be, but first wanted to see if anyone had other suggestions or definitive ways to know that it is indeed the motherboard.  One of my concerns is that I order the new motherboard and replace it only to find out that the problem was actually the power supply.  Based on the Dell documentation, this situation doesn't seem to suggest a psu problem, but I'm still in denial about the motherboard.  I've also read some things that suggest it is difficult to test a Dell power supply because it is proprietary.  Any suggestions would be appreciated.  

Answer : Problem: Dell Dimension will not power up

Normally a flashing power button light means bad PSU, which is not proprietary.  They put in 250w PS usualy but you could easily put in a 400W one.  Buy a power supply from somewhere, try it first and if it doesn't fix it take the PS back.  40 bucks is way cheaper then a MB and easier to.