Let me know if it worked

I think U should try for Windows Update that will take some time and then after this u get the option for the hardware update where may be u get the right drivers for ur graphics card. These drivers are also has digital signature.

May be ur problem is solve out.

Buddyjust try to use this,it's a old trick I had posted once a long time back here-

Locate the following entries in the registry:

HKCU\Software\Microsoft\Windows\DWM\Composition set to 1 (32-bit DWORD)
HKCU\Software\Microsoft\Windows\DWM\CompositionPolicy set to 2 (32-bit DWORD)

and then restart the Desktop Windows Manager Session Manager service (DWM) from the command prompt:

net stop uxsms
net start uxsms

This is only of use if you have a DX9 and PixelShader 2.0 enabled video card but for some reason Vista doesn't enable Glass.
This will not work if your graphics card does not support these technologies, as Aero Glass is dependent on them.

The minimum specifications to qualify for Aero Glass according to Microsoft is:

Support for DirectX 9 graphics with a WDDM driver, 128 MB of graphics memory (minimum), Pixel Shader 2.0 and 32 bits per pixel.

I dont know the source it was save on my harddisk for source take a look at my old posts.