Problems executing I.Browsers(Application Error)

[ShingujiSakura]

Greetings,
I have a friend suffering from some problem I haven't experienced before,so I need to request some help.Upon connecting to the internet,he tried to use I.E/Firefox(he has these two) to surf the net.Problem is,rather than the browser,an error window stating 'Application Error' appeared,and after that,the PC becomes extremely slow/laggy.Can someone please tell me what could be wrong with his PC?I tried calling the local internet service provider,but they said Application Error has nothing to do with the service.Please help.Thanks.

[glc]

Scan it for malware. You will need virus, trojan, and spyware scanners.