I would suggest escan, costs �6.99 from amazon and is updated all the time. Norton really slowed my system down so i went for this instead and it's been great. It includes just about everything in the Norton internet suite which costs �50 (firewall, mail virus scanning, blah blah blah)
As said above, Norton can seriously hog your system. I now use AVG (www.grisoft.com), which has a great FREE version... Remember to run a solid firewall too.... www.zonelabs.com for example..... (another great free product)
as i said above i use grisoft and have it set to update daily.
a firewall is also important as stated above.i used to run zonealarm but the newer version at the time clashed with some software - i switched to sygate firewall which is also free !
broadband ads bug me where they sell their products with free anti-virus and free firewalls - who cares ? you can get them anyways !!!!!
I bought Panda Titanium 2 years ago on recommendation and would never change it now. Once downloaded, a few easy sttings then you just forget it as it updates itself sometimes 3 times a day and neutralizes the 'nasties' instantly. I haven't been attacked once since I've had it as nothing gets past the little bear!
My last one was PC-Cillin and let in so many bugs that almost wrecked my computer so this one is a total joy.
Of course it's wise to give your computer a complete scan and not to do anything to invite problems but as you can tell I can't praise Panda enough.
http://www.pandasoftware.co.uk/products/titanium2004/
I tried the free AVG and its OK. Trouble is, it tells you when a virus is already on your PC and to find it. I now use Trend Pc-Cillin. No trouble at all. All viruses etc are put into quarantene for me to delete. Ok, it cost money, but you get what you pay for. I have trouble free broadband, no worries. :o)