When does the Windows Aero Effect Work?

Hi,
I recently figured out when the Windows Vista Aero effect be enabled. First it was some 4 months back that I installed Windows Vista Business by running the OS start up from my existing XP OS. That time I chose a new drive on the hard disk and the installation went fine. I logged into the Vista OS and I tried a lot to enable the Aero Effect. But, there was no option. I thought the installation itself was not right. Checked the setup logs, but could not find anything related to the Aero effect.
After 2 months of this OS being used, one fine day it started giving me problems. I was able to log into the Vista OS, but it was slow and the moment I tried to access any file it used to BLUE SCREEN. I got many variations of the Bluescreen codes. So, the only option now was again to re-install Vista. Other than this problem, i should say Vista worked like a charm. It was pretty fast too.
The second installation had to be done. So, this time I tried to install VIsta by booting the OS from the CD. I continued to install the OS by connecting my NIC to the router for internet so that the setup will automatically get all the required Updates while installing the OS. After the setup/installation was done from the bootable OS CD, the first thing I observed was that I could see the Aero Effect enabled.
So, now I conclude that if anyone doesn't see the Aero effect after installing Vista, then it means that they have started the Vista installation from an existing OS. Get the Vista Aero effect by installing the OS from the bootable OS CD.

thanks,
-KK