OS X Yosemite not booting after 50% loaded

Hey Guys, wondering if anyone could help me.

I just purchased a new mac, and while installing some new software I accidentally moved the .usr files into a different location. I'm still getting comfortable with the mouse and interface as I come from Windows. Now the issue is, I tried moving them back and a pop up appeared which said "moving files".. but nothing happened. It was like this for at least 15/20 minutes, and the loader bar was not moving.

I decided to restart the machine in the hope I can log back in and just move them into place. But now the machine gets to the username login screen. Once I enter my password the loader bar goes up to 50% and then halts.

Could someone please advise on what I could do to fix this?