My new cable-modem service comes with McAfee's firewall program. Do I need that in addition to the firewall that the Windows XP Service Pack 2 put on my machine?
Run only one firewall at a time -- keeping two active will complicate any troubleshooting without making Windows any more secure.
Of the two options, the McAfee firewall is more comprehensive. It will detect when any program on your PC tries to send or receive data from the Internet and ask you if that's okay, while the Windows firewall will only stop a program from opening its own port (a dedicated channel of online communication). Should your computer become infected by a virus or spyware, the McAfee program can stop those intruders from spreading themselves or stealing your data -- but it can't remove them.
The usual advice is to go with the most capable firewall. But I have heard from enough readers tired of thumb-wrestling with their security software to think otherwise. If you're comfortable with the built-in XP firewall, already run anti-virus software (as you should!) and are picky about your downloads, stick with that.
Put another way, confused users are more likely to make mistakes that leave their computers vulnerable. When in doubt, go with the security program you understand better.
Should my laptop's hard drive sound like it's sometimes speeding up or slowing down?
Generally, yes. Given how little attention is paid to keeping most computers quiet, a little whirring from the hard drive is normal. A harsh grinding noise, however, can be trouble. To investigate, run Passmark Software's free DiskCheckup program (www.passmark.com/products/diskcheckup.htm). Click the "Get Info" button at the top of its window to run tests; if they don't report an "OK" status for all of the disk's attributes, the drive is probably due for repairs.
-- Rob Pegoraro
Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or firstname.lastname@example.org.