QA strange Web site has taken over my browser's home-page setting, and now I can't switch Internet Explorer back to my old page.

AYou unwittingly allowed malicious code into your PC. Now you'll have to clean it out.

First, run a virus check using your anti-virus vendor's latest virus database. Next, download and run an anti-spyware utility to check for hidden programs on your computer. One newly updated spyware scanner, AdAware, is reviewed on Page 8, but in cases of severe infestation you might need to run more than one.

You can prevent such mischief by being careful about what sites you visit and what links you click. You can also block common browser-hijacking tactics by disabling ActiveX and Java in Internet Explorer, although that also would stop legitimate Web-site functions. In IE's Tools menu, select Internet Options and click on the Security tab. A third option is to try a freeware add-on to IE called StartPage Guard (www.pjwalczak.com/spguard/index2.php), which will prevent other sites from touching your home-page setting.

My new Gateway desktop is supposed to have a 120-gigabyte hard drive, but Windows XP lists a capacity of 111 gigabytes. Do I need a BIOS upgrade or something?

No. The difference is because hard-drive and computer manufacturers use different measures of a drive's capacity. A "hardware" gigabyte totals 1,000,000,000 bytes, while any software you use will define a gigabyte as 1,073,741,824 bytes. That difference means that a 120GB hard drive will show up in Windows as a 111GB disk.

-- 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.