Just so you know ... I did go ahead and try System Mechanic - a fully operable 30 day trial - that claimed it was compatible with Windows 8.1. After running all the scans, it corrupted so many files - my system was herky-jerky, slow, and I RECEIVED, OVER THE COURSE OF A COUPLE OF DAYS, 2 FULL SCREEN wINDOWS MESSAGES ABOUT A MEMORY PROBLEM [i HAVE 16 gb, PLUS A DEDICATED VIDEO CARD] Sorry, CAPS LOck ON. I tried all sorts of fixes ... system did run better after I uninstalled the program, but there were still like 2 dozen PCI-related processes running under Task Manager that I never saw before. After a System Restore point operation, it was a little improved, but got worse again. I just resorted to a complete format and rinstallation of Windows and software. Much better!!
Beware of this product!
I am going to be patient and wait for a word from Norton before I try anything else!