It makes a product consumers don’t buy, and often are unaware they own.

But despite its low profile, InstallShield Software Corp.’s revenues topped $30 million in 1998, and the firm ranked among Inc. magazine’s 500 fastest-growing private companies for the past two years.

Schaumburg-based InstallShield develops software that other software makers, such as Microsoft Corp. and Symantec Corp., buy to help users install their software—from games to word processing packages—automatically on their home computers.

InstallShield executives estimate they have an 80% share of the installation software market. Media Metrix Inc., a New York-based firm that ranks home software ownership and usage, listed InstallShield as the sixth-most-frequently used software and the eighth-most-frequently owned software—outranking software mainstays like Microsoft Word, Office and Excel, and even many versions of the ubiquitous computer solitaire.

Through a partnership with Redmond, Wash.-based Microsoft, InstallShield gets an early look at new Microsoft operating systems and software so that it can develop easy ways for consumers to install the new products on their computers.

‘‘Our relationship with Microsoft is simple: They are interested in assuring that our software works on their new versions, because if it doesn’t, then the Windows application can’t be installed,’’ says Viresh Bhatia, InstallShield’s 33-year-old CEO. ‘‘We have a technical relationship. There is no financial relationship.’’

There are few other firms that specialize in installation software exclusively, and few software developers want to spend the time and money to develop installation programs in-house, Mr. Bhatia says.

Because getting a software product from development to market quickly is critical to its success, most software firms prefer to buy installation software rather than have developers reinvent the wheel. As a result, Mr. Bhatia foresees continued growth for his firm, and has set an ambitious goal of $500 million in annual revenues in the next five years.

That represents a lot of software. InstallShield is not custom-designed, but sold as an off-the-shelf product for $795, with upgrades offered about twice a year. Even Mr. Bhatia acknowledges that to grow the company beyond his $500-million goal, it probably will have to develop other products in the next five to seven years.

Scott Wald, founder of Buffalo Grove-based Asap Software Inc. and a new board member at InstallShield, hopes the 240-employee firm will expand beyond its current narrow product niche.

Most InstallShield products are designed for Windows, in part because of the Microsoft partnership, although InstallShield also makes software for Java and Internet applications. Mr. Wald would like to see more of the latter kinds of products, as well as software that makes it easier for businesses to install and configure identical software packages on multiple PCs. He also sees potential to sell directly to the end user.

‘‘No matter how things change, installation is not going to go away,’’ Mr. Wald says.

Mr. Bhatia says the development of InstallFromTheWeb 2, an electronic commerce extension, has helped businesses, as software companies that take orders online want their customers to be able to directly download and use the product from the Internet.

Company expansion, which has included offices in England and Germany, so far has been financed internally, from profits. But in order to meet the company’s aggressive goals, Mr. Bhatia says he may consider a public stock offering within the next three years.