International Business Machines Corp. is in talks to buy Sun Microsystems Inc., people familiar with the matter said, a combination that would bolster IBM's heft on the Internet, in software and in finance and telecommunications markets.

The two companies have a common interest in that both make computer systems for corporate customers that aren't reliant on Microsoft Corp.'s Windows software, and their product lines are less dependant than rivals' on Intel Corp.'s microprocessor technologies. The two companies are also strong...