memtest is a great program to test memory. A loose ram stick can be the cause of the problem though I suggest checking all the ram sticks just in case :)
hmmmm.... I unplugged one of my RAM sticks and tried it and it started working... i plugged it back in, and it was still working. could 1 loose ram stick cause that? im kinda afraid to turn it off again. haha. I guess ill see if its fixed tomorrow. or if anyone knows of some free diagnostic programs i can run tonight, id…
pop open the lid and see if the graphics card is running/nothing is burned etc. Also another thing to try is removing the CMOS battery and putting it back in. Also as PolyHertz mentioned, some motherboards have a silent boot so if your hd is gone might not be booting into anything (though usually you see a blinking cursor)…