Ok so, you're using the Windows 7 upgrade advisor.
The Aero user interface (read: fancy transparent window effects) require that your hardware meet certain minimum specifications. Microsoft state these requirements as:
A DirectX 9 Compatible graphics adapter with support for Pixel Shader 2.0 and a minimum of 128MB of Video RAM.
So basically, your graphics card or your onboard graphics chip does not meet this specification. Likely, it either does not have Pixel Shader 2.0 or it has less than the aforementioned amount of dedicated video memory. The upgrade advisor, in this case, is therefore telling you that you can run Windows 7, but not with the fancy glass looking window effect.
Solution? If you have a desktop PC, buy a new graphics card. If you have a laptop, dream on...