PC always POSTs, but sometimes crashes afterwards

[santanoa]

When I turn on my computer, it always passes the POST test but then right afterwards, just after it leaves the BIOS screen, it will sometimes shut down. Then when it starts up again, it'll say that boot failed. I have reseated and all the RAM and very recently had to change a graphics card because the fan died. This is a home-built computer.

Thanks in advance

 

[warhead0]

Are any of the components overclocked? if not, this could be a PSU problem.

 

[nekulturny]

Can you give us detailed specs? Overclock settings (if any)? PSU brand, model, etc. OP system? More information is needed to help you with this. Also, the error message quoted verbatim.

 

[santanoa]

Asus P5ND Motherboard
Intel Core2 Quad 2.66GHz
2GB x4 DDR2 RAM (not sure clock speed, probably around 800MHz)
Nvidia GeForce GT 520 1GB DDR3 (NEW)
500GB HDD (not sure of frequency)
Corsair 550W PSU (80+ copper efficiency)
Windows 7 Home

The computer is about 3 years old and has no overclocked components