Honestly, that sounds like malware at work, or the result of malware at work. Is there a restore point that can be used to get the system to a date and time before the problem occurred? If you can't run anything or at least copy tools onto a USB key and ferry them over from another machine, you're left really with that or a repair install, unfortunately.
If you need to reinstall, you can access the system offline using a bootable PE environment (like BartPE or make a real WindowsPE environment using the WAIK tools) that can boot from a USB key or a bootable CD/DVD. These could offload files from the damaged windows install to a removable USB drive or another hard drive in the computer before installing Windows again.
MCTS Windows Internals, MCITP Server 2008 EA, MCTS MDT/BDD, MCSE/MCSA Server 2003