1.Press Alt+Ctrl+Del and get Task manager
2.Find explorer.exe task in process tab and select and end the process
3.Select folder option in my computer>Tool and select view and tick the 'show hidden file and folder' and unmark the 'Hide protected operating system file' and ok
4.Go to operating system installed drive (Most probably 'C' drive and find the explorer.exe in windows>system32 folder and delete it. (Note: Do not double click to open the drive instead of that select it from address bar)
5.If you have removable disk plug them pressing shift key and select drive from address bar.
6.Delete the auto run file and other unknown .exe files.
Now you are free from 'Mahasona' Virus.