Mary Kirsch used to ask some local high school kids for advice whenever she had computer problems.

"The problem with them was, they grew up and went to college," said Kirsch, who runs a financial consulting business from her Sewickley home.

She found a more reliable specialist two years ago. Jay Armstrong of Computer House Call now helps her with Internet and wireless connection issues, software and hardware problems and, increasingly with "bugs" -- the so-called spyware and viruses that infect most machines, threatening privacy and hindering productivity.

Office workers can rely on in-house, information technology departments to keep their computers running. But home users are left alone to face sudden shutdowns, layers of pop-up ads and slow performance caused by malicious software lurking on the Internet.

Like Kirsch, most just want to work with their computers and don't care to learn how they work. So they call pros like Armstrong, who has worked with computers for 27 years and started his Sewickley-based business three years ago after a friend pointed out that plenty of frustrated computer users need help at home. Computer House Call now has five employees and about 4,000 clients across Allegheny and Beaver counties. Armstrong's partner, Ed Abbott, is starting branches in Philadelphia and Cleveland.

Dozens of local computer repair services are fixing home computers across Western Pennsylvania, and corporate chains like Best Buy, with its Geek Squad service, and Circuit City and CompUSA are selling residential services. Geeks on Call of Norfolk, Va., started as a small business five years ago, has 205 franchises and expects to move into the Pittsburgh market within a year.

"The whole growth of the on-site computer service industry has been phenomenal in the last few years," said Geeks on Call spokesman Matt Nelson, although he could point to no industrywide statistics.

There are plenty of reasons for the growth.

"As the complexity of hardware has grown, people are realizing that they can't do these things by themselves," Nelson said, explaining that years ago, most home users didn't have to connect wireless networks and attach several peripheral devices to their computers.

The software issues are more vexing and dangerous. Spyware that creeps onto a computer with or without the user's permission -- yet in most cases is perfectly legal -- can track moves online and send popup ad windows or "adware," change personal Web settings and find bank account and other personal information that can open the door to identity theft.

Computers clogged with malicious software are tying up increasing amounts of time for repair firms. "On a typical day, where we have 40 to 50 machines in for service, better than half of them are here because of spyware," said Jude Daigle, owner of Computer Connections Inc. in Greensburg.

While businesses tend to go through the problem once, and then put in firewalls, home users tend to take longer before they learn to protect themselves, Daigle said.

Spyware started to become a nuisance about a year ago and became an epidemic in the spring, Daigle said. He typically runs three software pieces to clear the offending software off a system, and if that doesn't work he "wipes and reloads" -- removing the operating system, reloading it and adding upgrades and protections. The average repair of this type costs about $150.

Fred Carini, owner of Professional Touch Computer Service and Repair in Carnegie, normally charges $105 for his first hour of work and $65 after that but he's set a $200 flat fee for computer system cleanings. That includes keeping the computer for seven to 10 days if needed to make sure no hidden glitches are left. "Some viruses are triggered to go off on Halloween or the Fourth of July or on a certain midnight," he said.

Plenty of software programs are available to clean and protect systems. It's up to the user to carefully read agreements before downloading any online software, to scan regularly with a virus or adware scanner and to install a firewall and configure it so that only permitted connections are made, said Jason Rafail, an Internet security analyst with the Software Engineering Institute at Carnegie Mellon University.

Kirsch, with some coaching by Armstrong of Computer House Call, has learned to run debugging programs every three days and to back up her records on compact disc. "This is just a problem that we have to face nowadays," she said.

Daigle of Computer Connections said there needs to be more effective regulation of spyware, because just like the hundreds of spam messages that fill e-mail lists every day, spyware is a time-waster and an invasion of privacy.

"Companies that put spyware on a machine should be held liable for it, just like on the no-call or no-fax lists," he said.

What is spyware

Any application that tracks online behavior without the computer user's knowledge or consent.

It can pop up ad windows, change home pages and other settings and in its worst form can lead to identity theft.

It infects nine out of 10 computers connected to the Internet and has eclipsed viruses as the top threat to online privacy.

Protecting your system

Many corrective software programs are available for sale or download. Here are some no-cost tips for minimizing the problem from Hal Hanson of Hal-Com Inc., a Cleveland information technology firm with local clients:

Firefox is an Internet browser with a built-in popup blocker. Go to www.mozilla.org for the download.

Use www.OpenOffice.org to open Word, Excel and PowerPoint files received via e-mail or disk; it won't allow a Microsoft-related virus to run.

Use Zone Alarm as a personal firewall, which notifies the user of potential attacks. It's at www.zonealarm.com. Also, AVG Antivirus will protect against viruses, at www.grisoft.com.

Malicious software can be removed with Spybot Search and Destroy, at www.safer-networking.org, or Ad Aware at www.lavasoftusa.com.

Sources: Computer Connections, Hal-Com Inc.