Poor graphics performance on one of two displays
I've a strange problem, solution to which I couldn't find anywhere on the net, nor could I solve it myself to this point.
Short version: after messing with power saving options, my notebook's LCD is stuck in some kind of lower-performance graphics mode, whereas an external display works as usual.
Long version: I'm using two displays (separately): sometimes it's my notebook's LCD, sometimes I plug in an external one via HDMI. I've used this configuration for almost a year with no problems. But a few days ago I decided that I'd tweak power saving options. I did this on the notebook's display, and, AFAIR, unplugged to an external power source. Since then, I believe, even when the notebook's plugged in, the performance as for the graphics on the built-in display is poor, e.g. the Win7 logon screen looks like a highly compressed jpg - choppy, and DivX movies aren't playing smoothly. Also, transparency on Aero is disabled, though Win7 isn't able to detect any problems with that. As soon as I close the lid and the external display takes over, everything goes back to normal.
I've tried changing the power options back to the original, to no avail.
Any ideas as to how to make it work again?
If you need any more details, I'll be happy to provide them.