It is mandatory to install into USB Drive?

For the main license yes, then you can purchase an additional license to install into your hard disk.

Anyway keep in mind that license is NOT transferable, so in the case you change computer or hard disk you will NOT able to MOVE the HARD Disk license to the new one!

the best tip is to install Livetraker onto a removable drive (Ext HD/SD Card/USB Pen) and use it everywhere: it’s that easy!