Dan Hennessey received an e-mail from someone he knew. He clicked on the attachment, which looked like a Web page link. No page opened.

Hennessey (freshman-international politics) learned shortly after that he had inadvertently set a computer virus to work.

The virus, known as Myparty, is a recent worm outbreak that multiplies through infected computers by sending itself to addresses in e-mail folders.

Hennessey learned his computer had a virus when his Norton AntiVirus utility caught the problem, but the virus had already sent copies of itself out.

The e-mails have the subject "new photos from my party!" and ask the reader to click on an attachment and print pictures from the party. The attachment, called www.myparty.yahoo.com so it appears to be a Web site, is actually a virus.

Computer users can avoid the virus by not opening the link.

There are two variants of the virus listed by Symantec, a company that makes anti-virus software. One version can add a "Trojan horse" to a computer, making it possible to hack into the machine.

The virus has not noticeably slowed down the Penn State e-mail servers, said Kathy Kimball, director of computer and network security. She said students should invest in an anti-virus program and update it regularly to prevent virus problems.

"They need to know that this is a problem that's not going away . . . the longer they put off actually getting good anti-viral protection, they're a risk to themselves and others," she said.

Students can go to cac.psu.edu/infotech/virus.html for more information about viruses and virus protection, and to learn about getting free anti-virus software. Penn State's new contract with Symantec makes Norton AntiVirus available to students for free.

"Hopefully we've now made it a lot easier because you don't have to pay for it," Kimball said.

The Myparty virus also infected the computer of Kirstin Kapustik (freshman-administration of justice). She said had not been warned about Myparty, so she clicked on the attachment.

"It was yesterday, (Tuesday) morning, and my roommate had gotten some (Myparty e-mails) too, and I opened it before she had the chance to tell me not to," she said.

Kapustik said the virus just "seems to be really annoying." She said she has not found any damaging effects on her computer.

Hennessey said he's received about 30 to 40 Myparty e-mails from people his computer sent the virus to. The machines he inadvertently infected sent the virus back to him because his e-mail address was stored on those computers.

"I tried to tell as many people as I could not to open it but just delete it," he said.

He said he updated his virus definition files and he thinks his files are clean now.

"I scanned with it just to make sure there's nothing left," he said. "Hopefully I got everything."