XP-64 allows RAM usage over 3.12 GB and if your motherboard supports it you can probably go up to 8 or maybe even 16 GB. (Vista-32 is hard coded to top out at 3.12 GB, which is why I mention the number)

Something I wasn't aware of until recently, but most BIOS map hardware addresses starting at the 4GB mark and working down, even if you run a 64-bit OS. You should look in your BIOS for an option to remap hardware up above 4 GB to make sure you'll be able to use everything.

The other side of this is that this BIOS switch doesn't help if the OS is 32-bit. We had three ppro systems with 6 GB but 32-bit XP. (Why? Chain of bad assumptions starting with the system builder) The BIOS switch was flipped to remap memory and the side effct was to limit availabe memory to 2.0 GB. Stop remaping and now we have 2.4 GB addressable. Someday when all the hardware we have has 64-bit drivers we'll be able to use the additional 3.6 GB. Poor Ppro.

That's half the answer. I don't know if the 64bit Vegas will run on XP-64. I'm betting it will, but I'm not betting money.

Rob Mack