Blinking power supply, ..motherboard issues?

[bravebird20]

i have an hp a1220n desktop computer. within the past few months the heatsink fan had been quite loud, especially after running programs that demanded a lot of the cpu. i also recall getting frequent "power surge" messages when connecting an external hard drive that i've used a few times. last week my computer failed to come on and there was only the power supply light blinking. i read a tip about placing a fan near the back of the computer for a minute to start the power supply and this has been working, however i wanted to completely fix the problem.
i purchased a new power supply and still and yet, the computer does not turn on
i guess it's not the power supply because i just bought a new one....is it the motherboard? if it was the motherboard would my computer even be working after using the fan?
help, help!

 

[jsc]

The new PSU might not be good either. It could be DOA out of the box. That happens more often than you think, especially depending on what brand it is.

 

[bravebird20]

well after getting a new PSU and installing a new motherboard (used one though)...this darn system still will not start!!! i have no idea what's wrong but i still have the same symptoms...nothing will start, no fans, no computer screen, no bios...nothing....and the light on the older PSU still continues to blink (the newer PSU has no light)
i'm guessing it might be the CPU but why is it that the CPU will work (and the system will cut on) when i apply a fan to the back of the PSU? i cannot continue to run my system that way, as it overheats....anyone have any sort of advice or ways i can check which components of the system are faulty?