I have a Dell Inspiron 15, running Windows 7. A while back I noticed my computer started lagging every few minutes. This affects only video as audio works fine. The lags stops if I move the cursor, or press any button.
At first, I didn't care much, since I noticed it came and went. The weird part though was that it only happened when I was home, and not anywhere else. A friend then suggested it might have something to do with my WiFi. So I disconnected, and lo and behold, the lagging stopped.
I tried monitoring the Task Manager to see what changes during the lags, and I saw that the dwm.exe process memory usage jumps to 200 MB, which might be the cause of the problem.
I tried disabling Aero, but it didn't do anything. Someone suggested to copy the dwm.exe file from another Win7 laptop, but that sounds a bit risky.