I purposely disabled Aero, but after reading some informative posts and finding that most functionality in Aero uses graphics card instead of CPU, it was better off enabled. Doesn't sound like the same issue reported, but to re-enable it, I used the following:
1. Windows + R key to launch Run dialogue window.
2. Type in "services.msc", then click ok.
3. Locate "Desktop Window Manager Session Manager".
4. There should be a column for Status, indicating if the service is running. Mine displayed no value indicating service was not started and Startup type was set to "disabled".
For me, I needed to:
a) Right click the "Desktop Window Manager Session Manager" and select Properties.
b) Change "Startup Type" to Automatic.
c) Click the Start button under Service Status.
This kicked in straight away.
Info about Aero that made me change my mind:
Post by Shawn 'Cmdr' Keene \[MVP\] on:
http://answers.microsoft.com/en-us/windows/forum/windows\_7-desktop/windows-7-taskbar-color-not-aero/3ca1e3b1-0262-49ab-a199-6d38858eb39e