UninstallWinClient.exe is in the LDMAIN share of the Core Server. You use this to perform the uninstall.
You can send this out using landesk but remember that you may see a fail as the agent gets removed. If you use a command via Manage Scripts you can use the ,ASYNC option so it doesn't wait for the task to complete.
Also remember that an uninstall will force a reboot. Last time I tried, using /NOREBOOT as a parameter worked to stop it, but if you install the landesk agent before a reboot has happened you will likely get a broken agent after the next reboot as things are marked for deletion on the next reboot.
MarXtar Ltd/MarXtar Corporation
LANDESK One Development Partner
The One-Stop Shop for LANDESK Enhancements
That is spot-on MaxTar.