Smart Defrag Error “System Error! Exe file is corrupted and can’t run

My PC was running fine but two days before some “Smart Defragmenter”, which I never had installed, imitated a system scan and detected a lot of various infections on my PC. While Smart Defragmenter is running, it blocked the ability to run anything executable on my PC as the program says that they are corrupted.
Whenever I try to run them they give the error message

Exe file is corrupted and can’t run. Hard drive scan required Scan hard drive”
Can anyone please tell me the solution to remove this monster out of my PC.
