Windows 7 BSOD Code a1

Hi,
If your overclocking then please return to default values until the source of bsod is found.
Bugcheck 1A means a memory management error occurred which led to the BSOD. The details of this crash shows that the error occurred in a Page table which relates to virtual memory.
To rule out that your Pagefile hasn't become corrupted
Go to Start and type in sysdm.cpl and press Enter
Click on the Advanced tab and then under 'Performance' click settings, Advanced again then finally Change. Turn off the pagefile reboot and then re-enable it.

BiosVersion = V22.2
BiosReleaseDate = 12/19/2011
I checked on your bios updates and although you have updates stretching to version 23.2 you only need consider up to version 22.5. Above this the updates are for Win 8 so not needed. I also note that version 22.5 has memory stability updates:
Link Removed
Please double check I have the correct download for your motherboard.

netr28ux.sys Thu Feb 26 02:49:17 2009: Ralink RT2870 series USB802.11n Wireless Adapter Driver (you may have a different manufacturer) Is this something you've added? I don't see any driver on the support page:
http://uk.msi.com/support/mb/990XAGD55.html#down-driver&Win7 64

Check over the other updates that relate to your system on the above support page.

If after making the above changes you still get the bsod then you need to test your RAM.
Windows does have it's own memory testing app but it can often miss errors and the best app for the job is Memtest86. The latest version of which can be found here:
http://www.memtest.org/

To run Memtest86 you need to either burn a copy of it to disk or use a USB stick. If you look down the page you'll eventually find the latest version and it's associated downloads. If your burning to disk choose the pre-compiled iso zip. If your using a USB method then the corresponding download is the auto installer for a USB stick.
Once you have Memtest86 on the media you selected you'll then need to enter your bios and change the boot order so that the machine will boot from either the disk or stick you have Memtest86 on.
Run the test for at least 12hrs if possible unless it becomes clear that there is a issue. If there is a problem with the RAM you'll see the errors pop up in red so you can't miss them.