Reoccurring Blue-screen On Windows 7?

i bought this PC 2 years ago, i experienced a bluescreen now and then but at this time i didnt really care to look into it, as i didnt know much about PC`s Anyways, since about 2 months i bluescreen almost every second day.99% of the time i bluescreen while playing a game. (Such as TF2).I can tell when i am about to bluescreen, the sound starts to "crackle", with every third crackle i experience a little bit of a short lag (i would even say, its like a really short freezing but only just a milisecond). I ran Memtest and Checkdisk, Harddrive and Memory seem to be fine.My PC is free from malware.I started to read the minidumps out:They always show 2 or 3 different drivers causing the lag.One of them is ALWAYS ntkrnlpa.exe. The other drivers usually differ.Some driver that often shows up too is halmacpi.dll.

Specs:
CPU: Intel Core i7 920
Mainboard: PEGATRON IPMTB-GS - Intel X58 Chipset
GFX: ATI Radeon HD 5570
3 GB RAM

I might wanna add, i am using WLAN Netgear Stick WG111v3 Here are the results of my latest BC:

060412-29140-01.dmp04.06.2012 21:49:57IRQL_NOT_LESS_OR_EQUAL0x0000000a0xfffffffc0x000000020x000000000x82ebf68bafd.sysafd.sys+27b1cAncillary Function Driver for WinSockBetriebssystem Microsoft� Windows�Microsoft Corporation6.1.7600.16385 (win7_rtm.090713-1255)32-bitntkrnlpa.exe+4165bntkrnlpa.exe+7b68bntkrnlpa.exe+7d46fntkrnlpa.exe+770cfC:WindowsMinidump�60412-29140-01.dmp8157601144.224

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