1. Make sure the new HD is on the lowest numbered SATA port (check data cable and / or BIOS)
2. Right Click "My Computer" / Manage / Disk Management
3. Right Click on the new drive and Select Properties / General Tab and Label the Volume as "C-Boot" or something so you will always know this is the boot drive, hit OK and shyt down PC.
4. Install old HD to 2nd lowest SATA port
5. Check boot order in BIOS and make sure new drive is first and boot PC
6. Repeat steps 2 and 3 only label the old drive so you will always know what that is .... say "D-Old Files"
7. Right click again and if you don't like how it's partitioned, you can delete all partitions / volumes.
8. Create any partitions you want and format.