Internal hard disk drive not found??

I have an x51 r2 desktop...i-7 4770 8gb ram...standard stuff.

So my computer can not recognize my hard drive when i boot up my computer..I get an error saying internal hard disk drive not found. I even went out and bought a new HDD, still same thing.

This all started a few weeks ago, my computer started running slower and slower with an occasional freeze here and there. I went to restore my computer to see if that would help.. In the middle of restoration, it failed because of error on hard drive. Ever since then I could not boot it up. It just keeps booting then restarting and booting and restarting... what do i do?!?!? PLEASE HELP!!1