I only have 512 as well, if you run Office 2007 B2 TR, you will notice extreme lags, try using GeoShell instead of explorer, it kills lags, and you still get glass, the only problem is that GeoShell doesnt support the new file locations for Desktop, Documents, etc. Besides, if it runs San Andreas, i would think it would run Aero, just my thought though

I have a Socket A Sempron at 1.8GHz and a GeForce FX 5200 w128MB and i can run vista fine, the only problem is with explorer's memory usage. Try using GeoShell, you can still get the glass, and some of geoshell's features dont work properley on vista but somebody will fix that sooner or later.