Re: Upgrading to 64 bit
Vista/7 can take up to 192GB RAM and the actual max limit on a 64-bit system is 16EB, which is way too much and no such hardware is capable of that yet...and probably not for at least 2 decades to come.
Your 4GB RAM on a 32-bit OS is 3.25GB Max, but with the PAE, it reaches 4GB. However, the full advantage for today is between 4-8GB RAM. I personally have 16GB RAM, and I know I'm good for lots of years to come.