Panicky computer users all over the Washington area are scrambling to protect their machines before a highly destructive computer "virus" known as Michelangelo strikes tomorrow.

Local software stores reported yesterday that they were selling out of special programs that detect and remove the virus. Callers were swamping hot lines that advise on how to foil the electronic saboteur, which enters computers surreptitiously through a floppy disk and orders it to wipe out stored data on March 6, the birthday of the famous Italian Renaissance artist.

The virus has been found and removed from computers in places as varied as the Ramada Renaissance Hotel on Ninth Street NW, House of Representatives offices, Potomac Electric Power Co. and the National Institutes of Health.

"The phone lines have been bombarded by people. ... They're scared," said Chris Jollie, a software specialist at CompUSA, a large computer store in Rockville. An Egghead Software store on L Street NW reported that anti-virus software was selling out almost as fast as it arrived at the store.

John McAfee, chairman of the Computer Virus Industry Association, said that his group has been receiving more than 100 reports of Michelangelo infections a day from around the world.

Emergency inspections have shown that the vast majority of machines do not carry the virus -- only three of 7,000 machines at the House of Representatives have been found to be infected, for instance. Still, many computer owners expressed nervousness that their computers will rank among the ill-fated ones, and they are working against a deadline of midnight tonight to ferret out the saboteur.

"I'm having to send out an army of personnel," said Craig Pritcher, director of office technology at accounting firm Ernst & Young, which has about 200 personal computers in its Washington offices.

FBI chief William Sessions yesterday issued an alert about Michelangelo, which was first detected last year and is believed to have originated in Europe. "The FBI urges computer operators to use appropriate security procedures to minimize the risk," Sessions said in a prepared statement.

Outside the D.C. area, the virus has been detected at such far-flung locations as the New Jersey Institute of Technology, a Miami office of the Justice Department and the Department of Energy's Sandia National Laboratory in New Mexico.

Created by an unknown programmer, the virus infects only computers built to the IBM standard. Its creator crafted it to spread as floppy disks are exchanged, then lie dormant inside each computer until the user turns the machine on tomorrow. The virus then activates and erases data stored on the machine's high-capacity hard disk.

To date, experts have identified more than 1,000 separate strains of computer viruses. Some simply flash whimsical messages on the computer screen, but the common denominator is that they are unwelcome intruders that can seize control of a machine.

Experts say it is unclear how prevalent the Michelangelo virus is compared with other strains.

But it is by far the world's best known, due to a wave of coverage in newspapers and television that was triggered by news that a small PC manufacturer had accidentally sold 500 computers containing the virus.

Neil Schubert, director of systems for Ramada Renaissance hotels on the East Coast, became concerned after reading media accounts. Yesterday morning, after obtaining anti-virus software, he checked 40 machines at the chain's hotel on Ninth Street NW. One, installed on a secretary's desk, was found to contain the virus.

After determining that the machine contained no crucial data, he decided to advance the machine's internal clock to March 6 to see how the virus worked. The virus immediately began wiping out data -- "it bombed out the hard disk," said Schubert. He said the hotel now plans to institute regular checks for viruses.

In recent weeks, a number of companies have been offering free software that targets only the Michelangelo virus. But David Stang of the National Computer Security Association advised against using those alone because they would leave the computer vulnerable to other viruses.

Several computer managers said that the Michelangelo scare is having the positive effect of focusing attention on an issue that many have not taken seriously. "It drives home the fact that people really need to be worried," said Hamish Murray, director of information systems for the House of Representatives.

Tony Kaculis, director of information systems and technology for the Washington law firm Steptoe & Johnson, said he and several staff members came into the office at 6 a.m. Saturday to scan each of the firm's 500 PCs. They found no cases of Michelangelo, but the sweep turned up eight computers infected with another virus.

Potomac Electric Power Co. has directed its employees to check the company's 900 PCs carefully. So far, six cases of the Michelangelo virus have been reported to Kenneth Cohn, Pepco's manager of computer services.

Cohn said he is still concerned that the inspected computers could be reinfected. Asked if he was confident about the company's ability to get through tomorrow, he replied, "Confident is too strong a term, {but} we think we've taken more than adequate precautions."

Experts recommend the following steps to safeguard against viruses:

Reduce practices by which viruses can spread. These include the frequent exchange of floppy disks and the indiscriminate transfer of software over telephone lines from computer "bulletin boards."

Make backup copies of computer files, so that if a virus strikes the information can be restored.

Use software that detects and wipes out viruses. This is being offered over phone lines by some of the larger computer bulletin boards.

The Michelangelo virus can be temporarily foiled by leaving a computer off on March 6, or by altering the machine's internal clock so that it never reads March 6. In that case, however, the virus remains in the computer.