Vista 64Bit with 4GB of DDR2 800

My setups are

Q6600
2x WD500GB Raid 0
4GB DDR2 800 (maybe 2GB)?

Should i go with the Vista 64bit and get 4GB of DDR2 800? or should I stay with the XP and get 2GB of DDr2 800?

I use the system for video encoding most of the time at the back ground wile i do other things.

thank you.

Vista 64Bit with 4GB of DDR2 800

That's what I'm running now and I'll up that to 8GB soon.

Right now DDR2 is dirt cheap but that won't last too much longer.

You could also stay with XP and have >4GB if you get the x64 version.

can you run xp 32 bit with 4gb? I didn't know if that was the limit or not.

I running 4 gigs with 32 bit Vista Business , it shows 3.54 gigs....runs fine