Donate your old computer to charity, and you may be donating personal details of your life as well. As growing numbers of computer owners are discovering, it takes more to erase a computer file than hitting the "delete" button. Growing numbers of businesses are coming to the rescue.

The new products have names like "Cybercide," "Wipeclean" and "DataEraser" - names that leave little doubt about what the software is designed to do.

The problem is as new as the products designed to eliminate it. In the old days of computing, said Bill Adler of CyberScrub, hard drives were very small.

As a result, when you deleted a file, it was usually soon overwritten by another entry. In contrast, he said, today's hard drives are huge. "I just bought a laptop that has got a 30-gigabyte hard drive," he said, "and the chance of overwriting that data is slim to none. So, just recently with these large storage mechanisms, this problem has really come to the forefront."

And companies have come forward to help. Jim Reinert of Ontrack Data International says there are two ways to delete a computer file successfully. You can smash the computer to pieces or you can use an overwriting software program like the one his firm offers. "A slang term for that," he said, "is a scrubbing software. It literally overwrites the old data that is on your drive, and the end result then is your drive is put back into a state of factory condition, a blank state."

Mr. Reinert said people have often donated old computers to charity when they bought new ones. Few, he said, realized what they were giving away when they did. "A local television station purchased three used computers at various thrift locations," he said, "brought them to Ontrack Data to see what we could recover on those drives. We have been finding everything from medical records to social security numbers, finance, very personal information that is left on those computers."

As that kind of publicity has spread, CyberScrub's Bill Adler said, business has really picked up. "We have a lot of individual clients," he said, "but we do a tremendous amount of business in different fields, such as health care, which has new directives they have to follow for patient privacy. We have a huge market in the financial institutions, people doing online banking."

Ironically, most companies offering "data deletion" software today began as experts in data recovery. Jim Reinert said Ontrack Data International used to boast it could recover data from computers harmed in floods and fires. Today, he said, the company boasts its eraser software can sweep all data from any machine.