In Windows, when upgrading from php3 to php4, it may be found that you are getting a 'module not found error' or something similar.

This is the result of an incorrect registry setting in Windows.
Try this - preferably before hurling curses telepathically at M*crosoft ;-)

Open Regedit and look for the following key:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\W3SVC\Parameters\Script Map

NOTE: The ControlSet number. In my case I had 2 keys, ControlSet001 and ControlSet002. In each of these, I had a mapping to a previous installation of PHP and not the current installation.
Delete these, or change them to point to the directory of your current PHP installation, in my case;

'c:\php\sapi\php4isapi.dll'

I have no idea why there are more than one controlset, maybe it has something to do with the number of users set up on my machine. What I do know is that IIS looks at ALL of these control sets and sets its mappings according to what it finds there. I also know that after removing these spurious mappings, my system is now ready for a clean install of PHP 4.05.

If anyone knows what these extra registry settings are there for, please let us know.

Happy PHPing folks!

Neil J. McLeish