When I run scan disk for virus , it took long time going through the file 1381 file under my c drive. When I open it , there is tons of file which I don't recognise, can I delete all of them?

If I run the disk clean up, would it delete all the necessary file to run the window system?

You can probably delete the folder 1381. But to be sure, Rename the folder and test your system. If everything is fine, then delete.