Can’t finish install of Norton Antivirus

I have a computer that was brought to me with a slew of ad-war, mal-ware and viruses. I started to fix it by running ad-aware, spy-bot and hijack this. These three work fine and it appears that everything is cleaned up however, I can’t complete the installation of the Anti-Virus. The program installs but when the Norton Antivirus Configuration Wizard appears, the next button does not work. It does not say “not responding”, it just sits there forever. In addition, if I run the configuration manager from the dos prompt, it also appears but none of the buttons work. Any deas? Thanks