You can use Upgrade version to install Pro but it would be a clean install since the path is not supported for an in-place Upgrade. But a "fresh install" is what you said you wanted anyway.
Back up your files externally, make your Recovery Disks so you have a path back to factory condition, or
save a Backup Image of the entire HD first.
Boot the Windows 7 installer, choose Custom Install, then Drive Options (Advanced) to Delete all partitions not needed, following illustrated steps given here:
Clean Install Windows 7
If you Delete all partitions to create New ones and Format, the installer will issue a 100mb System Reserved boot partition which conveniently places the
Repair Console (normally only on the DVD or Repair CD) on the F8 Advanced Boot Tools menu. Partition as you wish and Format before installing to first OS partition.
The installer is mostly
driver-complete, with newer arriving quickly via optional Windows Updates. Just in case, have your Wireless driver on flash stick or CD so you can get online quickly. Then
enable hardware driver auto-updating and check for optional Updates several times.
Any
drivers still missing in Device Manager can be found on the Support Downloads webpage for your model computer or device.
Driver Install - Device Manager
Install updates and then programs slowly over time to gauge performance changes after each. Don't let any programs write themselves into msconfig>Startup as they slow startup, become freeloaders on your RAM/CPU and can spy on you. I only allow AV and gadgets.
Startup Programs - Change
Use a lightweight free AV like MS Security Essentials which works perfectly with Windows 7 Firewall.
http://www.microsoft.com/security_essentials/
When it is finished, clean and order the HD perfectly using state-of-the-art free CCleaner Disk and Registry tabs, then Puran boot-time defragger after adding it's Intelligent Optimizer on Additional Operations tab.
CCleaner - Free software downloads and software reviews - CNET Download.com http://download.cnet.com/Puran-Defra...-75115626.html
Finally save a Windows 7 Backup image externally so you never have to reinstall again, just reimage the HD (or replacement) using DVD/Repair CD with the stored image.
Backup Complete Computer - Create an Image Backup