Actually not hardware issue, its whether or not the software supports a vista environment. Most established programs nowadays support vista. I find it hard to believe that current adobe software are unable to run on vista since i have adobe acrobat professional on a vista machine and there are no problems with it.

So to goes for autocad 2009.

Depends on manufacturer. My workplace now have have 2 still run on windows xp since some of our programs werent designed for windows vista.

Worst still is that we need 2 use laptops and most laptops were designed with drivers only for vista and not xp. Fortunately dell and lenovo foresee this and had their laptops compatible with both xp and vista. Acer unfortunately doesnt do this.

Also the downgrade only applies for vista business and vista ultimate, u dont see home premium or basic getting this function.

Actually when vista first came out, it was worst then windows xp but after sp1 i would say its on par with windows xp but i like vista new security feature where they implement LUA which is very important for a business environment. Not so for home.

Maybe your PC too old so wasnt designed for vista.