[SCVirus]

Quarentined just means they are in an area which they arn't going to be automaticly executed at startup. Delete all the quarentined items unless the 'viruses' are bound with importent files. Depending the virus(es) said by the scan depends the cource of action you should take. From the whole spreading thing i'm thinking not a virus but a worm of self-spreading trojan, so in either of those cases the first thing you should do is update your security patches. If it is somekind of trojan i would suggest having all the email for the office run view remotely off of a non-windows machine with a virus scanner. Other then that the only real way to get comprimised is 0day sec holes and social engineering, asuming your websites (if any) are securely coded.