I want to change the default directory into which Windows install new programs.
This can be done in hkey_local
machine--->software--->Microsoft--->Windows--->current
version-->ProgramFilesDir.
The problem is that once you change it Outlook Express stop working!!
Odd as it seems Microsoft acknowledge the problem but offer no solution
Is there a way to overcome the problem?

Many of the OE components are registered within the registry using the
%ProgramFiles% variable, which becomes incorrect if you change the
default path. You might try performing a search/replace within the
registry to correct all the path information related to OE.