I've heard a few people say that a 32-bit OS cannot mathematically handle 4GB, and then they went on to describe something in more detail than I born to understand.
At the moment, I run 2GB of RAM on 32-bit vista, with a view to upgrade to 4GB in a few months. On the other hand though, I have also heard people say that 32-bit Vista can handle up 16GB of RAM.
Note, I am on 32-bit Vista Ultimate
Basically, I'm after a definitive answer as to whether or not my current 32-bit Ultimate will happily handle 4GB of RAM.