Aptiva 2153E2A

G'Day All,
Got this problem! The system I am working on had a virus, the owner said that he got rid of it but strange things have been happenning since. System seems to work allright except when trying to get onto the net and browse. I can hook upto the ISP with no problems but 95% of the time can't read anything (page cannot be displayed. Have low level formatted and re-installed Operating system twice but still the same problem. The net through another machine to the same ISP works fine. 2 questions
1. Is there a place in the CPU that holds instructions that could be corrupt through the virus problem encounted earlier?
2. Is there a chipset on the MOBO that the Virus has corrupted?

I have tried everything that I can think of, new HDD, Power Sypply, Ram, another CPU 166Mz but the problem persists

Thanks

Hope someone can help

Paul <IMG SRC="smilies/confused.gif" border="0">