Upload & Sell: On
You are confusing memory with storage.
Memory is RAM and is hardware limited by your processor/buss width.
Storage is hard/optical/ssd drive and is limited by your operating system.
You should just add another drive (and drive letter), perhaps as an external USB or Firewire drive. You can stack as many drives as your OS allows drive letter assignments.
Your plan will not be affected by XPs single-drive space limitation.
I doubt anyone has 1.5TB of memory connected to their personal computer. Storage perhaps (I have about 4.5TB on-line at any given time), but not memory.