yeah, many viruses block the installation of antivirus programs...
you can try different antivirus programs, Norton for example has the option to check for viruses before installing, the virus signatures are not the newest then but it´s worth a try. another option is to connect the HDD to another system and scan it then.
if you need to access/save important data on the HDD use a Linux live distro like Knoppix and boot from CD or USB-stick, you´ll be able to access the files then....
p.s. please use a more meaningful topic name next time...
