Edit: I called Microsoft before about upgrading to 64-bit and they said not worth buying unless you have over 4GB of ram, even for gaming it will not make a different. Plus they told me that they made a a patch so windows vista 32-bit now see 4GB of ram.
Windows Vista 32-bit can see all your RAM, it will show it in properties, but it still has same RAM restrictions. I have 8GB of RAM in my system, Vista 32 shows I have 8, but it can still only access 3.2GB of it.
I have 32 bit installed along side 64 bit cause of some old hardware I still need with no Vista 64 drivers =/, will go 64 only once I get upgrade.