Having two antiviruses installed will cause conflicts.
Please uninstall McAfee, it's known to cause BSODs. Use the McAfee Removal Tool
to uninstall it completely.
Download and install a fresh copy of MSE, recommend MBAM for additional security.
Run a full scan with both (separately) once downloaded, installed and updated.
Update your graphics card drivers to their latest.
Click on the Start
► Control Panel ► Programs ► Uninstall a program ► Uninstall ATI related stuff. Delete remnants of its driver using Driver Sweeper
Install the latest from the manufacturers website.
Driver c:\windows\system32\drivers\atikmpag.sys (126.96.36.19999, 184.50 KB (188,928 bytes), 4/04/2011 5:05 AM)
Run the System File Checker that scans the of all protected Windows 7
system files and replaces incorrect corrupted, changed/modified, or damaged versions with the correct versions if possible:
Run Disk Check on your hard disk for file system errors and bad sectors on it:
Keep us posted