I tried running Vista Home Premium on my old Pent4 that has 2GB RAM and it didn't do well at all. However, when I bought a newer computer with 4GB RAM and installed (a complete version of) Vista Ultimate 32bit all was well.
I really wouldn't suggest running Vista, no matter what edition, on a computer that has only 2GB RAM. It will run but not well. You would do better running WinXP.