I've been running this 32-bit version of Vista for quite some time now, so I have accrued several files/programs/music/etc. And I hear that 64-bit OSs dont support alot of old (and sometimes not so old) programs/hardware/drivers. I'm only even going the 64-bit route so I can bump up to 8GB of RAM to better 5-box in Northrend. So I figured I would keep my old installation intact and just use the new one for whenever I need more than 4GB of RAM for gaming.