If the crashes are virus related and you're having that many problems then you need to look at why you're having so many issues.
i.e.
what websites are being visited?
what software is being downloaded and run and from where?
are unknown email attachments being opened?
are you sharing media with other machines e.g. cd's, floppys, usb pens etc?
is your operating system fully up-to-date?
who has access to your machine and what are they using it for?
To put it bluntly as long as you have antivirus software, which you say you do and you are being sensible about what sites you visit, what email attachments you open and what software is downloaded then you shouldn't have any issues.
Kaspersky is supposed to be very good, although I don't believe they do a free version:
http://www.kaspersky.com/
Are you 100% sure that your problems stem from viruses?
