So you're taking the 200GB HD thats in your xbox and switching it with the 80GB HDD that's in your PC?
I'm not sure if this is the best way, but without doing any in-depth research here's what I'd do..
1. Download XboxHDM v1.9
2. FTP files from Xbox C,E, and the EEPROM into matching folders
3. Create and Burn the ISO
4. Stick the 200GB into your PC while keeping the 80GB in also, so it should load Windows
5. Go into My Computer and Right-Click-->Format on the 200GB, Now it should be FAT32
6. Copy files from 80 to 200 (This will take a looooong time if you have a lot of stuff)
7. Take out 80 and check if the 200 works in your PC(loads Windows, has the files you want, etc.)
8. If it does, then take out the 200
and rehook up the 80 to PC
9. Turn on PC and put in CD that you burned XboxHDM ISO to
10. Follow this tutorial
starting at "BOOTING XBOXHDM ( First setup your computer to boot from cd):