"If you want to move from a 32-bit version of Windows to a 64-bit version of Windows 7 or vice versa, you'll need to back up your files and choose the Custom option during Windows 7 installation. Then, you'll need to restore your files and reinstall your programs. For more information about performing a custom installation, see Installing and reinstalling Windows 7."
Just confirming that it works, though I'm assuming that Pro to Premium works. Likely.
May wish to PRINT THIS:
My advice:
1. Backup/Export all relevant data to a secondary drive
2. Write down the names of all programs you use
3. After installing Windows 7 Premium 64-bit there may be an "OLD C" folder; if so, Google for how to remove that.
Installing Windows:
1. Install Windows
2. Install the motherboard MAIN CHIPSET driver, then other relevant drivers
3. Video driver from AMD/NVidia as applicable
4. Intel site can scan for updates as well (newer than motherboard sites)
5. Install software (you made a LIST hopefully)
6. Import/copy back data from secondary drive
7. Make an IMAGE BACKUP (after Activating Windows) to a secondary drive if possible. (Acronis True Image or similar).