If you know the application name and company you can find and delete application's registry entries manually.
1) Run RegEdit.exe,
2) open the branch HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\Uninstall
3) look through the sub-keys and find application' name or application' company name. Registry entries from the mentioned above registry branch contain "uninstall" entries that are listed in the "Add/Remove Programs" dialog. If you delete the problem application entry from that branch then it will be removed from the "Add/Remove Programs" dialog too.
4) Next, you can search "HKEY_LOCAL_MACHINE\Software\" and "HKEY_CURRENT_USER\Software\" branches for the problem application name (or company name). If you want to remove an application from your machine you may want to remove application entries from the mentioned above two registry branches.
Note: be careful - do not delete the entire "HKEY_LOCAL_MACHINE\Software\Microsoft\" registry key.
Also do not forget to create backup .reg files (menu Registry -> Export Registry File) before deleting any entry.