Which part is dead?

greets,

i built my new computer about a month ago and its crapped out on me yet again...

i posted here before when it was giving me problems not posting (link below )

it ran fine for a while on both sticks of ram (about 4/5 days without reboot) but it crashed and never booted again :S

i have tried clearing the CMOS.. having nothing plugged in.. etc.

i have plugged in an internal speaker, hoping it was trying to beep out an error code but even with no ram sticks in the motherboard i get no beeps.. (the speaker works!)

so im hoping one of you guys could tell me which part i should RMA (maybe both O.o)

thanks in advance

ps.

added specs incase you couldnt be botherd looking at my older post
ASUS M3A78-EM motherboard
AMD X2 7750+ black edition CPU
ATI 4850 gfx card
2x 2Gb Corsair ram (800MHz)
2x SATA HDDs (320GB, 120GB)
500w coolermaster power supply

just tried the things you suggested, nothing works...

i have noticed that when i hit the power button, the CPU fan seems to speed up for half a second then slow down for 2-3 seconds

very annoying.. wish me luck with asus RMA (which doesnt seem to exist in the UK)

thanks for your help batuchka

There's a build checklist here:
http://www.tomshardware.com/forum/ [...] -checklist

After the checklist, try this:

Pull everything except the CPU and HSF. Boot. You should hear a series of long single beeps indicating memory problems. Silence here indicates, in probable order, a bad PSU, motherboard, or CPU - or a bad installation where something is shorting and shutting down the PSU.

To eliminate the possiblility of a bad installation where something is shorting and shutting down the PSU, you will need to pull the motherboard out of the case and reassemble the components on an insulated surface. This is called "breadboarding" - from the 1920's homebrew radio days. I always breadboard a new or recycled build. It lets me test components before I go through the trouble of installing them in a case.
http://www.tomshardware.co.uk/foru [...] _13_0.html

If you get the long beeps, add a stick of RAM. Boot. The beep pattern should change to one long and two or three short beeps. Silence indicates that the RAM is shorting out the PSU (very rare). Long single beeps indicates that the BIOS does not recognize the presence of the RAM.

If you get the one long and two or three short beeps, test the rest of the RAM. If good, install the video card and any needed power cables and plug in the monitor. If the video card is good, the system should successfully POST (one short beep, usually) and you will see the boot screen and messages.

Note - an inadequate PSU will cause a failure here or any step later.
Note - you do not need drives or a keyboard to successfully POST (generally a single short beep).

If you successfully POST, start plugging in the rest of the components, one at a
time.

Very good chance you have a bad PSU. Coolermasters are not particularly good PSU's.