Not long ago, searching the Web for the name Craig Pratt turned up a photo on Mr. Pratt's personal Web page showing a pair of jeans-clad high-heeled legs in the air with Mr. Pratt standing between them. There were pictures of Mr. Pratt's various drunken exploits. There were messages from friends about his dating habits.

A few months ago, Mr. Pratt, who is 22 years old, suddenly felt the need to kill that online self. He had just landed a job interview at a San Francisco public-relations firm. "I started freaking out," he says, worried that his potential employer might discover his rowdy online identity at MySpace.com, the Web site owned by News Corp. where he had posted the page that kept turning up in search results.

So he created a brand new online self, composing a new profile that left out embarrassing photos. He also pays much closer attention to the comments posted by his friends and pulls down the questionable ones as soon as he finds them. He changed his favorite book from Honcho, the hardcore magazine for gay men -- a joke, he says -- to "the complete works of Charles Dickens."

But inventing a new self was much easier than killing the old one. He says he emailed MySpace, begging the site to take down his old page. Nothing happened. He sent at least eight more urgent messages to the site, including a note to MySpace co-founder Tom Anderson. Finally, he received a cryptic email telling him to write his user name -- "craigisanidiot" -- and password with a marker on a piece of paper, to take a photo of himself holding it up, and to email it to MySpace along with a note saying, "I wish to be removed from MySpace."

His bawdy old self finally disappeared. Dani Dudeck, a MySpace spokeswoman, says Mr. Pratt should have been able to get rid of the profile with just a few clicks of his mouse without having to email MySpace, but Mr. Pratt says that didn't work for him.

"Getting rid of your account is not an impossibility at all. People do it every day," says Ms. Dudeck. She says she wasn't able to track down the company's correspondence with Mr. Pratt but that his experience seems unusual.

People who have spent years leaving behind traces of themselves all over the Web are finding it's hard to erase them. Susan Amirian, a 54-year-old media professor in East Stroudsburg, Pa., has lost more than 100 pounds in two years and is trying to start dating online. But she had a lot of trouble getting a batch of pictures from her heavier days out of Google Inc.'s image archive. She emailed former employers and academic publications that had posted the old photos on Web pages and all agreed to take down the photos. Yet Google's image-search tool still turned them up for months, despite Ms. Amirian's emails to Google's help desk asking that they be removed.

Ms. Amirian, who was recently divorced, thinks that potential mates will find the old photos and avoid her. "They're going to Google me and come up with these monstrous pictures," she says. A Google spokeswoman declined to comment on Ms. Amirian's experience, citing a company policy of keeping communications with customers private.

Google and Yahoo Inc. decline to say how often they hear from people soliciting help with their disappearing acts. The companies say their typical response to such inquiries is that they can't help. Both generally send an email back explaining that the most effective tack is to talk to the person who put the material up in the first place, say spokespeople from both companies. "I think it's important to understand that Google taking it down doesn't mean it's off the Internet," says Sonya Boralv, a Google spokeswoman.

Still, search companies say there are rare cases in which they remove links to certain Web pages. For instance, Yahoo pulls down links to pages that show confidential information like Social Security numbers or credit-card data when it gets reports from users, the spokesman says.

Yahoo's position didn't satisfy a 49-year-old Portland, Ore., woman named Cecilia Barnes, who sued the company last year for $3 million in Multnomah County circuit court. In the suit, Ms. Barnes alleged that her ex-boyfriend posted fake profiles under Ms. Barnes's name in a section of Yahoo, which included nude photographs and Ms. Barnes's contact information at work. Yahoo eventually removed the profiles, but Ms. Barnes argued that the site should have done so earlier.

The case was dismissed, on the grounds that the Telecommunications Act of 1996 says Internet companies cannot be held legally responsible for material published on a Web site by a third party. Ms. Barnes is appealing the decision in the U.S. Court of Appeals for the Ninth Circuit. She declined to comment through her lawyer, Thomas Rask.

Matt Terich, a 32-year-old computer programmer in Seattle, recently discovered to his horror that his buddies had decided it would be funny to attach his name to a fake Amazon.com review of a sex toy. He stumbled upon the practical joke in May when he idly searched for his name on Google. The review turned up on the second page of results. When none of his friends would confess to the prank, he sent a note to Amazon.com's customer-service department: "As hilarious as my friends are, can you please take down the following comment? It shows up in Google searches and kinda bums me out."

Mr. Terich -- who was trying to start a business designing wedding invitations -- began to get desperate when days passed, and he still hadn't heard from Amazon. He grilled his friends, who finally confessed and took down the review they had posted on Amazon.

Last year, Heather Anne Hogan, a 27-year-old accountant in Braselton, Ga., ran into an old friend at a local restaurant whom she hadn't spoken with in years. Within minutes, the friend had asked about an awful date Ms. Hogan had recently gone on. Ms. Hogan was horrified when she realized the friend had been reading her blog, which came up in a Web search for her name.

So Ms. Hogan studied the techniques used by marketers to push Web sites higher in search results, like including one's own full name in the blog's title. Then, she did the opposite, taking her name out of certain parts of her blog and changing the way she posted links to family members' blogs. It worked: Her Web site quickly tumbled lower in results.

By last fall, she had experienced enough of obscurity and wanted to be seen online again. So she started a blog at a new site, without using all the tricks to hide it. The new site, heatherannehogan.com, comes up first in a Google search for her name.