Ntoskrnl BSOD

Hello, I recently built my first PC and I've started out with this error randomly. Mostly it happens when accessing one of my hard drives but the drivers appear to be up to date. Sometimes I get the BSOD when idling. Sometimes when shutting down my PC. I've checked my drivers (I Think). Ran Memtest (found one of my sticks to be faulty and replaced it) Bios is up to date as well.

My Specs:
CPU: [FONT=Verdana]INTEL|CORE I5 3570K 3.4G[/FONT]
Motherboard: [FONT=Verdana]GIGABYTE|GA-Z77X-UD5H[/FONT]
Ram Corsair Vengeance LP 4gb x2 1600 (mobo sets at 1333 so I "OC'd" it to proper 1600)
GPU: Evga GTX 670 4gb FTW and Physx 9800gtx
PSU Silencer Mk II 750W 80 plus silver
OS: [FONT=Verdana]WIN 7 HOME SP1 64BIT 1PK - OEM[/FONT]

[FONT=Verdana]Using a blue screen viewer all my shutdowns appear to be caused by ntoskrnl.exe+7efc0 but my google searches have failed to really help me. Only thing I haven't tried is re-installing my OS. I want to avoid that if possible.[/FONT]

[FONT=Verdana]I seem to be unable to upload minidump files.. need help with that too. Says I don't have permission.... which I should...[/FONT]
 
Is Windows fully updated using Windows Update manually and including all the optional updates? Are there any yellow exclamation points in the device manager?
 
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