Uninstallation of combo cleaner impossible

Hello,

This appears to be an administrator authorization issue: if the current account is (as it should be) a user account, restart under an administrator account (the easiest way is Ctrl-Alt-Delete, switch user).

Beforehand, check in the services (if you don't know where, search for services.msc) if there is an entry for Combo Cleaner; if so, set it to disable via properties, then click stop). It is likely that those people have added a startup entry that is more or less easy to find.
Download autoruns https://docs.microsoft.com/en-us/sysinternals/downloads/autoruns, once installed right-click, run as administrator, uncheck everything related to Combo Cleaner.
The only thing left, in principle, is to manually delete all entries, and there may be quite a few (Program Files, Program Data, Temp Folder, and dedicated Folder in C:\Users\"Me"\Appdata

A simpler Plan B: download Unlocker https://www.commentcamarche.net/telecharger/utilitaires/22737-unlocker/, which will integrate into the context menu, right-click on the stubborn folder, but this won't necessarily clean up the startup entries if there is one in the registry that points to an executable installed not in that folder but under C:\Windows.

To uninstall it:
>> Settings... Apps and features... Click on the "Combo cleaner" application.
2 buttons are present: Modify and Uninstall.
At this stage, you need to go through this page to proceed with this operation.

There may not be a startup entry (the "run" sections in autoruns or the "run" and "runonce" keys in the registry), and that's a good thing.

Regarding unlocker, you need to right-click on the stubborn folder (in this case, combo cleaner) and select unlocker.

In the left window, go down to delete, and then confirm; regarding a protected folder, the software is likely to throw a tantrum while processing for a certain time, and then send a message stating that uninstallation is impossible unless you restart: obey and choose stop/restart.

If you were unable to delete anything by proceeding this way, the only (bad) luck being that you didn't open unlocker from the context menu and right-click, but rather directly from its shortcut, and you might have selected the wrong folder, and then we won't be in a good situation...