Tilda

Earlier today my computer became infected with the Vista Security virus scam so I had to download a-squared to remove it. Once the computer had been scanned and everything quarantined, it advised me to restart the computer so I did.

As it started up again a message came up to say the infection had been removed successfully, however now I can't open any applications such as firefox, windows media player, Microsoft office or my security programmes. They're all .exe files and won't open. I managed to get IE by deleting the desktop shortcut and creating another however this is not working for anything else. When I tried to create a new shortcut for word a message came up saying "windows could not create the shortcut. check to see if the disk is full".

Can anyone help me figure this out asap? As you've probably already guessed I'm somewhat clueless with computers!
I can't download malwarebytes or anything else as they're .exe files so when I try to run them it can't find a programme to open them.