Okay so I was dowloading some torrents last night as per usual, then suddenly my PC (Toshiba Satellite Notebook) didnt let me open any new applications. I double clicked some on the desktop and from the start menu, no reposnse from anything... so I was like Ok I'll restart the thing.
When it rebooted, even the bullshit antivirus start-up screen that I couldnt get rid of previously displayed an error message saying it cant open

Aboslutey no apps will open whatsoever. Ive tried restarting 5 times. Windows is otherwise running smoothly and I can do most file managemt tasks still.
Can anyone tell me whats wrong here? Im guessing its a virus as it seems to be a really unusual problem... but I cant run virus purging software as no applications work

Will I need to format my machine? Help!