QIf I install Firefox, how can I make sure that it is the default browser? Should I uninstall Internet Explorer?

AYou should have no trouble making Mozilla Firefox (www.mozilla.org) your standard browser: When it first runs, it'll ask if you want it as the default.

Forget about uninstalling Internet Explorer. Microsoft doesn't allow this; it's possible to yank this program with some tinkering, but that's still a bad idea. Windows is a complicated house of cards.

The solution for most people should be to make Firefox the default while using IE only at sites that refuse to work in any other browser. Microsoft's Windows Update site is among that small number -- but if your computer downloads critical updates automatically, you won't have to fire up IE to visit it. Microsoft has directions on enabling automatic updates at www.microsoft.com/protect.

When I turn on my machine, it takes a moment for the antivirus software to kick in, even though the computer has already logged on to my Cox cable account. Is this a security risk?

It's a very minor risk, if any at all. Viruses -- unlike worms -- can't get on your PC by themselves. They have to arrive in e-mail, instant-messaging file transfers or another mechanism. Assuming your e-mail or IM program doesn't load before your antivirus utility, you should be okay.

Firewall safety against worms is different. Microsoft's Internet Connection Firewall takes a moment to start up, which can leave Windows briefly open to attack. The answer is to use another firewall, such as ZoneLabs' free ZoneAlarm, or to wait to plug in the cable modem until after Windows finishes booting up. (Microsoft's upcoming Service Pack 2 update for Windows XP will fix this issue.)

-- John Gilroy

John Gilroy of Item Inc. is heard on WAMU's "The Computer Guys" at noon on the first Tuesday of the month. Send your questions to him in care of The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or via e-mail to jgilroy@iteminc.com.