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My PC recently caught a virus that disabled my antivirus software and blocked my access to almost every antivirus Web site. What can I do?

Robert Lamar Duffy, Eight Mile, Alaska

Some viruses protect themselves by blocking security Web sites, antivirus programs, and other tools that could be used against them, including Windows' System Configuration utility (Msconfig) and Registry Editor (Regedit). They cleverly block antivirus Web sites by altering your Hosts file--a text file with no extension that individual programs use to assign a specific IP address to a Web page. In Windows XP, this file is in the C:\Windows\system32\drivers\etc folder; in Windows 2000, it resides in C:\WINNT\system32\drivers\etc; and in Windows 98 and Me, it inhabits C:\Windows. To correct the problem, double-click the Hosts file and choose Notepad or another text editor to open it. Delete any line in the file that refers to an antivirus Web site. Or simply delete the Hosts file; Windows re-creates it automatically with zero entries.

Now browse to an online virus scanner to check your hard drive and (we hope) remove the virus. A good one is Panda Software's ActiveScan (e-mail registration required). It uses an ActiveX control to check your system, so you have to use Internet Explorer.

To keep your system's defenses unblocked, change the extension of any utility's executable file from .exe to .com (which, like .exe, is executable). Thus, for instance, if a virus won't let you edit your Registry, select Start, Run, type command, and press Enter. At the prompt, type ren c:\windows\regedit.exe regedt.com and press Enter. Now the command regedt will launch the Registry Editor.

Change the System Configuration utility's executable file from 'msconfig.exe' to msconfig.com. In XP, this file is in the C:\windows\pchealth\helpctr\binaries folder. In Me and 98, it's in C:\windows\system. (Windows 2000 lacks this utility.)

Read Unreadable CDs

Years ago I burned thousands of photos onto CD-R discs using a Windows 98 machine. Now I find that I can't read the discs on my new XP-based PC. How do I get my photos back?

H.C. Lott Jr., via the Internet

You probably created the discs using a packet-writing application that came with a third-party CD-burning program, such as Roxio's Easy Media Creator (it may have been called "Easy CD Creator" in those days) or Nero Burning (aka Nero Burning ROM). Packet-writing software works in the background, so it's easy to forget--or never realize--that you're using it. These programs often use proprietary formats, converting to a universal format only when you "close" the session. If it doesn't close properly, the disc will be unreadable on systems without packet-writing software--and maybe on any PC with a different packet-writing program.

To address the problem, open a packet-writing program on your new PC. In Easy Media Creator, the packet writer is Drag-to-Disc (see Figure 1). If you use Nero Burning, the program is InCD (you may have to install it separately).

If you can view a disc's contents, close the "session" you just started. You will no longer need a packet-writing app to read that disc. If you don't have any packet-writing software, use the program on your old PC to open and then close the discs. If that computer is no longer available, open and close the discs in a packet-writing program on another machine.

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