' ... shows the programs.' - You mean the mapsets, don't you.
Click the uninstall button.
Select a mapset to uninstall.
If that works, do so for the other mapsets. If it does not work, there is likely a problem with the registry entry for that mapset.
If MSTK uninstalls all the mapsets, check the Control Panel>Uninstall Programs to make sure the mapsets are not listed.
If that is OK, reinstall Garmin's 100topo from the DVD/CD it came on - you mentioned installing the 100topo so I (we) assume you purchased the DVD/CD version.
If 100topo now works, then install 'my trails ....' - if not, call Garmin tech support.
If 'my trails ...' works, then install TXtopo.