If you are asked for a password when removing Trend Micro PC-Cillin, open regedit, browse to HKEY_LOCAL_MACHINE\Software\Trend Micro\PC-Cillin and either rename or remove the System sub-key. Then try the uninstaller again. It's just that stupideasy!

This doesn't work if you are already in the uninstaller being asked for the password and then remove you the key, so remove the key before starting the uninstall process.

Midas reports:

You can also use pcctool.exe for 2007 and older or tissprt.exe (or similar name) for 2008.

which will remove Trend Micro PC-Cillin without a password. You can find it in the installation directory.