After repairing a XP installtion that was not starting, neither the activation and Internet Explorer was working. Some users said on some newsgroup to repair the installation (!) or to re-register the some DLLs that were causing the problem.
But, bruce12453 gived a great answer:
Open control panel then add remove programs
Uninstall Internet Explorer 7 or Windows Internet Explorer 7 which ever shows
If that does not show:
Open My computer
Click tools-->folder options-->click the view tab
Choose show hidden files and folders
Uncheck hide protected operating system files
Click apply then OK
Then go to My computer
Open C:\windows\ie7\spuninst
Double click on spuninst.ex
Thanks, that solved the problem, after rebooting windows, I was able to active Windows and to re-install IE7.
-f.