Give this a whirl first to fix the exe file association:
Go to: http://www.dougknox.com/
In the left hand column, click: WinXP fixes
In the list that appears, click: File Association fixes
In the next list, click: EXE File Association Fix
Next, save the file to the Desktop
Go to the Desktop, and right-click the xp_exe_fix.zip file
Select: Extract all…
A folder: xp_exe_fix appears
Open the folder, and double click the xp_exe_fix.reg file
Allow it to run and the reg file to merge
Check this additional guidance on the website:
“NOTE: If your EXE file associations are corrupted, it can be difficult to open REGEDIT, or to even import REG files.
To work around this, press CTRL-ALT-DEL and open Task Manager.
Once there, click File, then hold down the CTRL key and click New Task (Run). This opens a Command Prompt window.
Enter REGEDIT.EXE and press Enter.”