HouseCall can only detect viruses already on your system at the time of your visit. Protecting your system against computer viruses typically requires two steps. First a scan of your existing system (which HouseCall does), then a continuous scan of all file activity (or real-time protection) which is done through the installation of antivirus software. If youan infected Word document attached to a new email or insert an infected diskette into your computer, HouseCall won't detect it.