Hello I am new and need urgent help, virus is ruining my business

I foolishly have all my business files backed up on a second drive on my system...yes I know, lesson has now been learnt.  Anyway my old AV program expired and again I did not renew, lesson learnt.  Ayway I was having fun with my son by changing me desktop pic to cute puppies by searching google for pics and setting them as desktops.  I clicked one pic and noticed my HDD going mad and then media player opened, I shut it down but noticed my pc acting strange, loads of HDD activity over the last 2 days.

 

Yesterday I purchased Norton 360 and it finds Ramnit.inf I scan and scan and it finds more and more, it has deleted loads of dll files and as a result my main software for my business no longer works and I am losing other files.  I formatted last night and reinstalled my Avid editor (I am a video editor) and again as soon as I installed Norton it found the Ramnit.inf and Ramnit.html.  I checked my backup drive and it seems this is where they came from, I have lost loads of work from my backup but I can not get rid of this virus.  I was up till 6:15am and am now quite depressed as my entire business revolves around this computer, I am getting desperate and really hope someone here can help.

 

So far I have scanned my entire system about 7 times and the last time I did this in safe mode after switching off system restore and doing a disk cleanup to delete all unwanted files.  The safe mode scan found 33 versions and fixed them but as soon as I booted back up normally the norton protection found more Ramnit.inf and as I type this it is popping up every few seconds.  Please help.

 

Thanks