Here are the requirements to run Aero.
Below are the areo hardware requirements.
1-gigahertz (GHz) 32-bit (x86) or 64-bit (x64) processor
1 gigabyte (GB) of random access memory (RAM)
128-megabyte (MB) graphics card
Aero also requires a DirectX 9 class graphics processor that supports a Windows Display Driver Model Driver, Pixel Shader 2.0 in hardware, and 32 bits per pixel.
For best results, you might also want to follow these graphics processor recommendations:
64 MB of graphics memory to support a single monitor with a resolution that is less than 1,310,720 pixels (for example, a 17–inch flat panel LCD monitor that has a 1280 × 1024 resolution)
128 MB of graphics memory to support a single monitor with a resolution from 1,310,720 to 2,304,000 pixels (for example, a 21.1–inch flat panel LCD monitor that has up to a 1600 × 1200 resolution)
256 MB of graphics memory to support a single monitor with a resolution greater than 2,304,000 pixels (for example, a 30–inch wide-screen flat panel LCD monitor that has up to a 2560 × 1600 resolution)
Taken from this site.
http://answers.microsoft.com/en-us/...-desktop/f731d7e2-8731-438a-a839-011597d8099a
Your old dell probably only has 8 mb of video memory onboard if that.