Windows 7: Automatically switching off Aero mode?

Hi - I'm having a problem with Windows 7 SP1 where, after a few hours, Windows seems to switch off the Aero theme by itself with no obvious cause. I can't seem to switch it back on, either, when I go into the Personalise menu - there's no option to change the colour of the glass as there usually is... only restarting seems to resolve things. What's going on here?

Hmm - just noticed WinSAT.exe was running in the background and hogging the CPU while this was going on - and then a minute or so later it switched back into Aero mode again! Weird... o_O;;

Did you Assess/Re-Assess your system with Windows Experience Index?
Did you recently update a driver?

If you did not run a assessment/re-assessment or recently updated a driver click the start orb, right click "Computer" and select "Properties"
After that scroll down to your system specs where it usually shows your WEI (Windows Experience Index) score. If it needs to be re-assessed then it will say "Your system needs to be re-assessed" or something simliar to that above your WEI score.
Click that and it will take you to the WEI page and assess/re-assess your system.

Thanks for the reply.
I didn't reassess it, no, but I think the graphics driver (Intel 4 Series) was updated not too long ago, so could that have been why?
The Windows Experience score page doesn't say it needs to be reassessed, but I'm sure the graphics score is lower than it used to be... When it was switching off Aero, was it reassessing it?

I believe so, but I don't think it should show a lower score during a re-assessment. Run an assessment and see what happens (if you haven't done so already). After driver updates I noticed score either fall or rise afterwards, for example, a 5.6 dropping to a 5.5 or vice-versa.

Thanks - will try this and see what happens!