With Ektron 9.3 SP2, Solr was updated to 7.4. As part of the Solr update the install directory folder was moved to <rootdrive>\Solr.
For instance, if you pick the install directory as "D:\Program Files (x86)\", a Solr directory will be placed at D:\Solr.
This is due to an issue in Solr 7 where Solr cannot start when the execute path contains parentheses like "C:\Program Files (x86)\":
There is currently no workaround and this should be fixed in a later version of Ektron's Solr. This KB will be updated with the details.