You're replacing it with a new one ?
Hmm, most new drives hold a lot more storage space than most old drives.
Unless you just HAve to replace it, I'd leave windows on the drive that you're already using and just put the new drive's jumper in slave mode, and use it for storage only.
Having a storage only drive proves to be the best route if/when you ever have to reformant, esp if you get a virus. A storage drive or different partition from the one you boot from could save your stored files, but booting from the same drive you store everything on usually doesn't.