Hey guys I just recently bought mixcraft pro Studio 7 and im trying to figure out how to create a decent sounding rock guitar. Im not satisfied at all with any of the sounds and was wondering if anybody knows some tricks or tips. I have my guitar plunged straight into the USB slot using that rockboand cable that came with the game. Could that be the reason why it sounds bad? 
I would suggest having a look at LePou's amp/cab sim VST plugins.  They're free and generally highly regarded.  Plenty of info out there for the googling.

I doubt the USB guitar cable is to blame, but a small audio interface such as the Focusrite Scarlett 2i2 wouldn't do any harm.