It might be that the game program hasn't closed and is still causing problems from the background.
From Troubleshoot problems with Windows Aero:
Some older programs might be
incompatible with Aero. When you run
the program, Aero might stop working
for as long as the program is running.
Closing the program should restore
Aero. To avoid this problem, check
with the manufacturer of the program
to see if there is a version available
that is compatible with Windows Vista.
And another possibility:
If you are running the Power
saver plan, Windows sometimes turns
off transparency automatically. If you
don't want this to happen, you can
switch to the Balanced power plan.
You might also verify the video card driver from the manufacturer's site (not Windows update).
EDIT
Found an interesting article :
My Vista Aero Glass Turned Itself Off, How Do I Enable it Again?
It lists a few more cases that you might like to check, but the text you'll find most frustrating is:
When Windows Vista detects that your
computer is running too slowly for
Aero, it will automatically disable
it. Normally once you close out of
some applications everything goes back
to normal, but sometimes you get
“stuck” with the Vista Basic theme,
and have to go in and enable it again.
This means that your game has taken too many resources to keep up Aero, and Windows just stays in basic mode afterward.
For more shortcuts for turning on Aero and transparency, see:
How to Enable or Disable Aero in Windows Vista
Jordan, what model of graphics card are you using, and what version(s) of the drivers have you been on while the problem has been happening?
The design of this site is such that I can't leave any information unless I provide it in the answer box as I don't have 50 reputation yet, but I'm having a similar problem with a VERY powerful system.
I don't remember the disabling happening for the first year or so I had the PC, which equates to two things in my mind, I hadn't added the 2nd graphics card then, and ATi's drivers were...less mature (not that that's a good thing). I haven't changed anything else about my system in that time, other than updates to common software products.
Specs that matter:
- 2x HD 5870 in Crossfire (2GB dedicated video memory)
- i7 920 @ 3.6 GHz on H20
- 12GB DDR3 @ 1443 MHz
- Antec CP-850 PSU
- Windows 7 Professional
I've checked CPU-Z, Hardware Monitor, CoreTemp my voltages and temperatures are near spot on...even my Corsair 750 Professional Gold isn't as close to perfect at load. I want this to be completely software related so badly, but considering I can't reproduce it on a notebook with considerably less power in EVERY way, I'm starting to think it's possibly related to a hardware configuration.
On the software side of things, I'm used to Aero disabling for games/programs that call the service to stop, then re-enable it after. I'm having problems with Aero disabling itself while using something as simple as Mozilla Firefox or VLC video player, which have had no issues in the past.
Drivers, CCC software, all up to date, I've tried with both Windows and ATi software set for both full eye candy and full performance, and I'm getting the same errors. It's odd that I can run a game like Metro 2033 at 5760x1080 with no artifacts, glitches, with Aero still on in the background, then I open one Firefox window or VLC window, and that dreaded yellow exclamation point comes up and I lose Aero immediately.
One thing I found very helpful in my quest to fix this annoyance is this little tidbit. Open your registry, find the following location (you create the Restart Aero and Command folder).
HKEY_CLASSES_ROOT\Directory\Background\shell\Restart Aero\Command
Create a new string in the Command folder, and leave it named (Default), then under Data, type the following:
CMD /C NET STOP UXSMS & NET START UXSMS
That adds the option to Restart Aero to the right click context menu when you're on the desktop. So now instead of opening up a CMD window to re-enable it, you can just right click and click. I created an executable file that just runs the same command as well, but I find this to work even better.
Hopefully this satisfies the answer portion in some way!
Best Answer
Actually, the reason Aero can prevent tearing without having to force VSYNC on in an application is because it is a compositing window manager. It draws the desktop and all windows asynchronously with respect to any running application.
That is to say, when you enable compositing in Windows Vista / 7 (it is always enabled in Windows 8), it will draw all of the windows using a copy of the last image that was swapped from back to front. The compositor (Microsoft calls it DWM, Desktop Window Manager) composites everything with VSYNC enabled, and because it draws using a copy of the last fully-swapped front buffer image for each window it never displays partially drawn frames. It does, however, have an unfortunate side effect of preventing really old software that was designed to draw into the front buffer exclusively from working correctly - but modern software does not do this.
In a nutshell, the DWM adds an additional layer of protection against tearing. One that will allow any application running on the system to draw at a rate irrespective of the display's refresh rate and still prevent tearing. On such a system, in windowed mode the only thing enabling VSYNC in OpenGL or Direct3D is good for is actually throttling back CPU/GPU utilization.
This is why adaptive VSYNC was created, the idea there is not to penalize applications that cannot sustain the display's refresh rate by forcing them into a lower factor of the refresh rate (e.g. 60 Hz --> 30, 20, 15, 10, 12, 6, 5, 4, 3, 2, 1) but to limit applications that are drawing faster than the monitor can display images from using an excessive amount of CPU / GPU power.