I have seen this before. Create a file called unhookexe.inf with notepad or another simple text editor, on another system and put the following in the file:
Version]
Signature="$Chicago$"
Provider=Symantec
[DefaultInstall]
AddReg=UnhookRegKey
[UnhookRegKey]
HKLM, Software\CLASSES\batfile\shell\open\command,,,"""%1"" %*"
HKLM, Software\CLASSES\comfile\shell\open\command,,,"""%1"" %*"
HKLM, Software\CLASSES\exefile\shell\open\command,,,"""%1"" %*"
HKLM, Software\CLASSES\piffile\shell\open\command,,,"""%1"" %*"
HKLM, Software\CLASSES\regfile\shell\open\command,,,"regedit.exe "%1""
HKLM, Software\CLASSES\scrfile\shell\open\command,,,"""%1"" %*"
HKCU, Software\Microsoft\Windows\CurrentVersion\Policies\System,DisableRegistryTools,0x00000020,0
Put the file on a usb drive or copy it to the hard drive. Right click the file and select install and you will then be able to run exe files again.