game screen keeps minimizing

[KaptainK714]

added a new 1TB drive to my computer last week had no issue with any programs until yesterday when my current CIV4 BTS game would minimize after about 4 minutes. This happens about 3 times then will stop for awhile.

Running Win7 ultimate, on home built system AMD athlon IIx4 processor. no virus on my machine per latest scan Malawarebytes and AVG.

Any ideas how to fix this

ps- my AVG is updating now but quite sure it wasnot yesterday