The Blaster virus and it's relation (Welchia I think) don't come from emails. They do not affect Windows 98/98SE machines, they are fairly harmless on NT but on Windows 2000 and XP they are deadly. There is a patch on the Microsoft website for NT/2000/XP - go here, then scroll down to find the fownload for your operating system:
http://support.microsoft.com/default.aspx?scid=kb;en-us;823980Note that if you are smugly thinking "I'm all right, I put patch 26 on a while back", Microsoft issued patch 39 in early Sept which supersedes 26.
btw also note that Microsoft NEVER send patches out via email - this week there has been a hoax patch purportedly from MS which in fact was yet another virus...
All Windows users should visit
www.windowsupdate.com once in a while (monthly at least) to ensure there are no critical updates - these are often the ones which viruses exploit.
For any "permanently on" connection you MUST have a firewall to prevent receiving this kind of virus. And the rate at which these worms are still active I would recommend everyone to have a firewall, even if only connecting for a few minutes at a time.
My firewall is currently being hit at a rate of 6 or more times a minute by traffic which I am pretty sure is Welchia. I reckon it's the volume of this traffic on the internet which is causing problems accessing sites sometimes.
A reasonable free firewall is Zonealarm. It does the trick quite adequately.
http://www.zonelabs.com/store/content/company/products/znalm/freeDownload.jspAnd there is a free virus checker called AVG which is also well thought of.
www.grisoft.com. But remember to keep it up to date!
www.symantec.com has a lot of info about worms and the current threats etc, as well as some free removal tools