QOur new portable DVD player won't play movies -- it turns on, but nothing shows up on its screen.

AThe problem turned out to be a little switch, flanked by "In" and "Out" labels, on the side of this player -- a discount Insignia model my co-worker bought at Best Buy. Its manual explained that this switch controls whether the adjacent audio/video plug will receive video from an outside source, such as a VCR ("In"), or send video to an external display, such as a TV ("Out").

The manual said the "In" setting should have put the DVD movie on the player's own screen, but that didn't happen until I switched it to "Out." That makes no sense, but mass-produced electronic devices can be like that sometimes.

There are two lessons here. One, you can't count on getting a quality product every time. Two, when something doesn't work, try flipping whatever switches are available, even if their labels don't suggest they could solve the problem. You're unlikely to damage the thing (provided none of these buttons are labeled "self-destruct"), and you might stumble across a case of mislabeling or crossed wiring.

My son apparently allowed the installation of a spyware program that took an hour to remove. Can I restrict my son's logon under Windows XP from installing any software whatsoever?

Windows XP Home provides only two types of user accounts: "Administrator" and "Limited." An administrator -- the standard option -- can install and do anything, while a limited user can install very few programs and can't tinker with system-level settings. For this situation, use a limited account; any programs that might be added under it can't claw their way deep into the system.

Microsoft's earlier consumer operating systems -- Windows 95 through Millennium Edition -- lack this option, making every user an administrator.

-- 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 rob@twp.com.