Hi and welcome to Geeks to Go.
I enquired on your behalf with the developer of TFC and my personal thanks to OldTimer...
Now regarding the issue with TFC(Temp File Cleaner) you may have inadvertently clicked on the mouse and before(and or during) TFC had completed its run, the actual prompt to reboot your machine was most likely hidden by the actual TFC GUI(Graphical User Interface)...which if occurs again you would merely click on the aforementioned GUI and drag across until the reboot prompt is visible.
If you had done this, all your file extensions would have been automatically reset to default by TFC.
So what you need to do now is manually reset your file extensions yourself, how to do so can be read here
I would delete whatever version of TFC you currently have and download a fresh copy from here
Now in the event you still encounter a problem running TFC and ensured you have followed the above advice...There may be a problem with your machines actual Hard-Drive, may be something like in-depth maintenance required for example. Either way my advice would be create a topic in this part of the forum:-
Hardware, Components and Peripherals
Or create a topic in part of the forum designated Operating Systems
, in the sub-forum for your machines actual Operating System. You will in turn(due course) receive appropriate advice from one of the excellent Tech Staff we have here in Geeks to Go.