HELP ME! AERO SUDDENLY DISAPPEARED!

After an automatic upgrade (I think) last fall, my AERO disappeared. Though
it still shows up on the list of choices under "appearance settings" (and the
AERO file exists in the themes folder) AND I have chosen VISTA theme, AND I
have enabled transparency, etc, I still cannot get it to work.

ALSO
My computer was preinstalled with Vista, bought last year, and more than
fulfills all requirements to run.
I have tried to "flush" aero using the rundll32.exe
Dwmapi.dll,DwmEnableComposition
I can run WINSAT, and it says I have LDDM

I have a dell Intel(R) Core(TM)2 CPU 6600 @ 2.4GHhz, 2046 RAM, 32 bit, ATI
Radeon X1300PRO 256MB driver version 8.31, DX10, 255MB video memory

I can find my way around a computer, but don't have any technical
background, so please respond! In simple terms! I have tried just about
every fix I could find on line!

ETERNALLY GRATEFUL!

See if any Aero-incompatible Software is autostarting each Windows
session.Those can prevent running Aero until they are not executed anymore.
( Apple Quicktime before 7.3 was such software for example )
use either Msconfig or the Sofware Explorer in Windows Defender to review
and disable autostart apps.

Make sure the following services are running:

Themes
Desktop Windows Manager

(Control Panel > Administrative Tools > Services)

[marz]

have you installed any new software recently? some programs, even if they are only putting an icon into the tray will make vista default to xp like scheme. this is becaused they cannot or have not been written to support aero
i suggest closing down any new aps which you may have installed recently and trying to get aero back via the personolize panel again. once the rogue proggie is closed down aero should come back.

Thank you very much. I have been beating my head against keyboard for
days. Installed sp1 on vista x64 ultimate and could not get aero or
glass back, so in turn could not even attempt dreamscene.

Desktop Windows Manager was disabled in services.

i solved this problem for me by checking that my system was using 32 bit
colours. Mine had been set by a program to use 16 bit and had left the
system as such.

Control Panel > Personalisation > Display Settings

or you can right-click on your desktop and select Personalisation >
Display Settings.

Hope this helps for anyone who couldn't solve this problem otherwise.