Windows won't boot with 8gb ram after reinstalling windows

[Naglis]

After installing new copy of windows 7 (sp1 ultimate 64bit) my windows won't boot (won't go past "starting windows" (freezes)), tried switching to my old RAMs (2x2gb) and it booted up fine, but whenever I switch back to my 2x4gb RAMs it won't boot.

What I tried:
Swithing the power suply off and on
Using only one stick
Mixing sticks (2gb and 4 gb) (6gb ram)
Tried to boot in safe mode (also froze)

Oh and before reinstalling windows, I had the same 8gb ram on my computer which had the same windows (7 sp1 64bit ultimate) and it used to boot fine.
Sorry for bad English, hope to get some help.

 

[Lutfij]

1| When posting a thread of troubleshooting nature, it's customary to include your full system's specs.
2| Have you made sure your BIOS is up to date?
3| Don't mix and match rams, this only adds to system instability.
4| If your system exhibits an issue when in BIOS then the rams are giving out. Try and run memtest86 for at least 10 passes per stick per slot to rule out the slot or ram module as faulty.
5| Go into your BIOS and see if the timings and frequency are as stated on your ram sticker or an X.M.P profile.
6| You may also want to recreate your bootable media for your OS to rule out a corrupt installer.