Computer BSODs frequently

So.. Everything begun when I decided to upgrade my computer to match nowadays games like Starcraft 2 which was lagging way too much in some cases..

First of all I bought a new graphic card, power supply and screen. (When I started playing games I noticed my computer makes some nasty screeing voice while playing?) After a few weeks my computer just died and wouldnt start up, found out my motherboard/CPU died.

So I went back to shop and bought new motherboard, new processor, new CPU, 4GB of RAM (later another 4GB too making it total 8GB) and new operating system (OEM Windows 7 Pro x64 , old one was vista 32 , formated both hard disks before installation).

After a day with new software/hardware my computer started BSOD:ing in like everything I did (opening folders, installing stuff), mostly "PFN_LIST_CORRUPT" or "MEMORY MANAGEMENT" as reasons.

I ran all kinds of memtests/hard drive tests with no negative results so I decided to open up computer and watch if I pulgged something wrong and found out there were second power cable slot capped in motherboard -.- When I plugged second cable to it my computer could do everything just fine before a new problem arise.

Half of times when I start up my computer it works fine for about 5 minutes and then programs stop responding and are unable to start leading to "Explorer.exe doesn't respond". If I try to restart explorer, computer BSOD:s with reason "SYSTEM_SERVICE_EXCEPTION". If I shut down my computer immediatedly after first program stops responding, it will shut down normally.
After I restart my computer it works just normally without any problems!

I have checked my drivers with like 3 different driver programs and downloaded latest ones I could find (except intel chipset drivers). Also programs wont start crashing if computer survives first 5 minutes or so.

So I'm asking what to do with these BSOD:s (and whats wrong with voices my computer makes while playing, is it normal?)

Remove Avast and replace it by MSE
Memory corruption is also the cause, one or more RAM modules may be damaged, test each module individually

Code:

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BugCheck 3B, {c0000005, fffff880056335de, fffff88007c6fd60, 0}

Probably caused by : aswMonFlt.sys ( aswMonFlt+25de )

BugCheck 4E, {2, 79015, 21ffff, 1}

Probably caused by : memory_corruption ( nt!MiUnlinkPageFromLockedList+8e )

Followup: MachineOwner

Thanks for fast answer! Replaced Avast with MSE, I'll post back if I meet more BlueScreens.