I ran the beta version with 1GB on three of my machines.
1) AMD 64 2800 with 1GB DDR 400
- office software, PowerDVD, Windows Media Player
2) Core 2 Duo E6300 with 1GB DDR2 8000
- office software, Matlab, TV tuner, PowerDVD
3) AMD XP 2200 with 1GB laptop
- office software, Power DVD
I don't know about games or more demanding applications though. They all run fine for what I need them to do so 2GB would probably be safe.