NIS2011 validation

Hi

Situation goes like this,I try to keep a clean system, keep fresh updates, don't mess around dodgy sites, or dodgy software.

but yet there are all sort of mild things, like a little white dot when my ATI driver loads,certain file fonts which turned blue without

an understandable reason,and top with my NIS crushing last week .

all that while the NIS scans even in a safe mode full scan giving me no warning .

So I would like to know which are the best ways to validate that my NIS2011 are not corrupted by virus's and spyware .