The following solution worked for me:
visit hxxp://support.eset.com/kb5824/#v10
(replace the XX with tt)
and follow instructions , but.....
delete all the FOLDERS in the location, not the free files
reboot... (all the features in eset will be red, don't panic)
Then....
enter to control panel, click in programs and features, then click on eset,
then, click repair/reinstall..
reboot your system...
Voila!! All green and the license wasn't lost