Many BSOD´s all the time, and startup problems

Hello people,

I am pretty new here and i have a big problem with my computer, since a month or maby two i get many BSOD ( some of them: Page foult in nonpaged area, Driver IRQL not less or Equal, System Service exepition, Reference by pointer, and some other...[cant write them down because bsod was so fast away...] ).

Here are my System Specs:

Windows 7 Professional 64 bit
ASUS M4A785TD-V EVO (sound onboard)
AMD Athon(tm) II 620 Processor 2.60 GHz
Kingston DDR 3 KVR1333 *4 = 8GB Memory ( two "old" [2 Years], and two new one´s)
750 GB Harddrive
Zotac GeForce GT 430 Synergy Edition

I hope you can help me with my problem.

Almost forgot : Sometomes if i get a BSOD and i want to start the computer again the cooling starts but (i think) bios dont starts because there is no "beeeep", and nothing happenes until i cut the power off . I have to try sometimes more than five times to get it started.

sry for mistakes i am from austria...

edit: i have done a memtest and i have reinstalled windows many times...