hi,first a litte backstory to my problem

my last HD broke a couple of weeks ago, i got the message "no boot device available". the HD was a couple of years old and i've been getting the
"disk boot failure" message from time to time with it. but everytime i've been able to get it to work by just checking the cables or waiting a few days.
but this time i handed it in to a shop who told me i had to replace the HD. so I had them put in a new one and everything was ok for like two weeks.

now to the issue.
First i got the "disk boot fail" rebooted and it worked.
but i noticed the computer was realy slow and it crashed. after reboot and some more crashes i got three differnt BSOD's:

one without any real info(or i dindn't pay attention to the first one),
one with a mention of ati3duag.dll,
and one "with kernel stack inpage error"

now i get the "disk boot failure" on every startup, i've noticed the fan dies down right before and I'm wondering if i might have a faulty power supply.

anyone have another suggestion or recognise the BSOD's?