Hard Drive filled to capacity virus like

Hi,
I have a computer that the customer reported that after being on the internet the computer started acting funny. One of the error messages before it stopped loading was Initialization of the help center failed, ms error # 21347024784. The hard drive is now full to capacity and will not boot. A svanreg /restore to an old date did nothing to improve the problem. When I boot with the me disk it shows the hdd maxed out. Is there a fix for this or do I need to restore the os.
Thanks