FSX

My computer is now started to kick me out of FSX, with the message, that it has run out of memory. I have 6gig ram and a 1gig graphic card.

I am running windows 7 Ultimate. I have windows 7 HP 64 bit. Should I change and will it be better. I believe somewhere I read that 32bit dose not recognize any ram above 3gig. The computer is not connected to the internet.
Any help and advice would be of great help.

Bsmyth