In a command prompt open up the registry editor:
c:\>regedit.exe
Browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
Here installed programs are listed by application ID.
Browse through them and look for the Display Name to identify the application you need to uninstall.
There will be a key called UninstallString, right click to Modify and copy its contents:
This value will be used in the command prompt, running msiexec.exe with the /i switch. /i configures the application.
Depending on the application, the uninstaller will run, which may be a GUI or another automated uninstaller.You should see the Application ID removed from the Uninstall reg key from above.