As Apple Computer Inc. enters its fourth decade this week, it faces a set of headaches that are relatively new to the company: the ones that come from being a top dog.

After spending most of its life as a respected but cultish small player, Apple has entered the mainstream, courtesy of the iPod. For years, tech industry watchers wondered if the company would even survive, as Apple’s share of the computer market dwindled to a sliver.

With the success of its digital music player and online music store, Apple now is finding itself accused of being a monopolist. French lawmakers are trying to make Apple stop linking its online iTunes Music Store exclusively to its iPod player, and music publishers are chafing at Apple’s refusal to charge more than 99 cents a track at iTunes. Both argue that popularity gives Apple unfair control over the market.

Even malicious software-writing hackers are showing an unwelcome interest in Apple’s Mac computer. This year has seen two “malware” programs designed to muck up the Mac operating system. Though the programs weren’t particularly damaging, antivirus software companies were quick to pile on with talk of how Mac is about to become the new “it” platform for hackers to attack.

These are the sort of problems that Microsoft Corp. usually has had to deal with as the tech industry’s biggest player.

“Once you get to be a certain size, you get to be a target,” tech pundit Rob Enderle said. “You can do pretty much whatever you want when you’re small, but when you’re the dominant player, the rules change.”

Computer maker marks 30 years.

Apple’s numbers are still small on the home computer side – it controls less than 5 percent of the market – but the company has arrived at a tremendously influential place in pop culture.

“Apple’s importance in high technology is grossly disproportionate to its market share,” said Owen Linzmayer, author of “Apple Confidential 2.0: The Definitive History of the World’s Most Colorful Company.” “Apple is considered by many the research-and-development company for the rest of Silicon Valley.”

Apple didn’t make the first computer, perhaps, but this was the company that brought personal computers to the masses and made the personal computer revolution possible with its early understanding of the importance of an easy-to-use graphic interface for computer users.

Decades later, the iPod is the latest and most profitable example of the company’s skill at turning technology into something that changes people’s lives. The world already had several MP3 players to choose from before Apple made its entry, but Apple’s product took it from a niche gadget class and transformed it into a cultural force.