XP Home upgrade to XP Pro - freezes when in windows

Hello,
just this evening I upgraded my XP Home to XP Pro - the installation worked fine and everthing seemed to be working until i logged on (as admin).

I can access the applications of my taskbar and i can click on the shortcuts in my immediate Start menu - however if i go into Program Files in any way or My Computer the comp freezes and explorer.exe goes to appx 99 CPU in task manager - I can end task explorer.exe and restart it and it unfreezes.

I cant right-click on desktop or use Search - however IE works fine as does Outlook express adn all the other programs I can get to without going through any folders or My Computer etc...

I know the easy way is to do a clean install but I have so many big apps that I need for school and lots of other important stuff I dont wanna lose.
I tried safe mode and still the same problem.

What are my options? and thanks.

 

anyone?

Need this fixed asap as I have so many things for school due.

 

You can try System File Checker (start, run and type in sfc /scannow) or a repair.

You may lose Service Packs and patches with a repair, and it's not foolproof, but with either way you won't lose personal files and apps.