A couple of quick things to try:
1. If Autodesk Inventor has its own uninstall program try that.
2. Sign on as the administrator, (via Safe Mode on XP Home, or
Ctrl-Alt-Delete twice at the welcome screen with XP Pro). Then go to Add or
Remove programs and try to remove the software.
3. Contact the Autodesk support.
If these steps don't work, things get tricky. You may want to get a 3rd
party registry cleaner. There's a free one named RegCleaner. It will allow
you to delete the Autodesk entries in the registry. This can be dangerous!
The alternative is to go in and edit the registry and manually remove the
entries. Try the easy stuff first. If you need to go into the registry,
reply, or repost your question.
Paul Shafer, MCDST