QMy wife and I have started getting spam that lists our own e-mail address as the sender.

ASpam just keeps getting harder to avoid. What happened here is that a spammer used "spambot" address-harvesting software to collect e-mail addresses listed on the Web and found yours.

The technique is normally used to put together a long list of addresses to spam, but spammers can also elect to make their junk mail look like it came from a real person. The return address on an e-mail is easy to forge, and a message sent with it won't get rejected by many common anti-spam filters.

The best defense remains keeping your address out of a spammer's database. If you have to leave your address on a public Web page, you can alter it so it's readable to a human but confusing to a spambot. For example, you could change it from "jgilroy@iteminc.com" to "jgilroyNOSPAM@iteminc.com."

The Center for Democracy and Technology recently did a study on how spammers get addresses. It's worth reading: www.cdt.org/speech/spam/030319spamreport.shtml.

I know that when you delete a file, the data remains on your drive. How can I ensure that nothing's left of a deleted file?

This is the time of the year when two strange forces collide: Readers do their taxes on their home computer and think about upgrading to a larger hard drive. But if you dump the old drive, can somebody recover your financial data from it?

They can, so you should use add-on software to finish the job. Your choice is whether to rub out individual files or scrub all the free space on a drive, just in case you have remnants of other sensitive data left around. Wizard Industries' SureDelete offers both options and is free to download (www.wizard-industries.com).

-- 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.