BSOD after gaming for about 20-30 minutes

About 2 months ago I built this computer and always played Call of duty Black Ops, MW2 perfectly fine with over 100 fps so heres my spec..

AMD Phenom ii x4 965
Asrock 880/GMH motherboard
ATI Radeon HD 4870
and 320 Gigs of Hard drive

Then all of a sudden I keep getting these BSOD's out of nowhere here is the error report..:


Problem signature:
Problem Event Name: BlueScreen
OS Version: 6.1.7600.2.0.0.256.1
Locale ID: 1033

Additional information about the problem:
BCCode: 124
BCP1: 00000000
BCP2: 85A7F01C
BCP3: B6762000
BCP4: FF000135
OS Version: 6_1_7600
Service Pack: 0_0
Product: 256_1

Files that help describe the problem:
C:\Windows\Minidump\050611-15568-01.dmp
C:\Users\Luke\AppData\Local\Temp\WER-28688-0.sysdata.xml

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C:\Windows\system32\en-US\erofflps.txt

HERE ARE ALL MY DUMP FILES:
http://www.mediafire.com/?6ys13n868155s35

http://www.mediafire.com/?stnzcj5t7cn7bua

http://www.mediafire.com/?xmdc1gn4bxmewuq

I read the dump file with BlueScreenVew and it said it is caused by 'halmacpi.dll' at Address 'halmacpi.dll+ef3f'

Please help I don't know what to do and i'm getting tired of these BSODS!