PC not booting

[HSK]

Hey guys, i need some direction coz im not too sure whats going on with it...yesterday and today when booting the PC, it doesnt get past post...freezes after the CPU check, and just says memory. but the mem test doesnt complete. when i rest via reset button, same thing. it only works when i unplug the power and re-plug then turn on.

I havn't messed with the bios, only recently for a while when i tried out the C.I.A.2 feature for about a week (but the it was at the lowest setting, and the computer was fine). i did buy 2 new ram sticks, but this was about 3 weeks ago and everything was ok then...only other things i can think of is a external hard drive i've added, connected via usb (which seems to turn on straight away when i power the PC). I still need to try booting from cold without it, too see if it's doign something. my power supply is quite borderline aswell for what i've got in the PC, but it's been running fine n stable for weeks.

any help is much appreciated

is there any program i can test the mem?

[peterb]

Memtest86++ - Google will find it for you.

[0iD]

Have you checked your ram voltages in the BIOS against what the manufacturer recomends for that particular make/model. Plus try taking them out & putting them back one by one, find out if one or all are at fault.

[HSK]

Hmm so i tired memtest, n left it for over 12 hours - 0 errors reported, so im thinking it's not the memory, i've unpluged the external drive and i'll give it a few days and see if it happens again. if it does prolly test the parts on the weekend when i open the machine.

[HSK]

and this might be abit of noob question, but im not clued up at all on ram - on post it says 800mhz. but in CPU-Z its saying DRAM frequency 400MHZ?

the voltages are at 2.0.v 5-5-5-18. although the rating on the manufac site is 2.2v 4-4-4-12. could i put up the voltage abit? worth the difference?

[0iD]

It's DDR2, Double Data Rate.