Pete Wells' aging computer doesn't support Aero. Should he upgrade his graphics card?
I like Aero, but not enough to bother upgrading hardware to get it. Many people don't like it at all.
The built-in Aero technologies give Windows a certain three-dimensional look, with semi-transparent window frames. Microsoft added Aero with Windows Vista, and kept it through Windows 7. It's on by default in both of those Windows versions--except for the Windows 7 Starter Edition, which lacks Aero entirely.
But it's a controversial feature--if you can even call it a feature, since it serves no practical purpose. All it does is make your screen look better. And to do this, it uses some resources, and thus slows down your PC a little bit. It's one thing to take a small performance hit for antivirus software, since it does a job that really needs to be done. But do you need a performance hit for something that just makes the screen prettier?
On the other hand, if your hardware supports Aero, and you like the look, and you're not trying to squeeze every last millisecond of performance out of your hardware, there's no reason to turn it off. I keep it on, myself.
If you want to turn off Aero in Windows 7, right-click the desktop and select Personalize. Select a theme from the Basic and High Contrast Themes section.
Microsoft chose not to include Aero in Windows 8. I don't know whether they did this to improve performance, or to make the desktop environment as unattractive as possible.