Washington ? Microsoft Corp. warned customers Tuesday about unusually serious security problems with its Windows software that could let hackers break into their computers to steal files, delete data or eavesdrop.

Microsoft, which learned about the flaws more than six months ago from researchers, said the only protective solution was to apply a repairing patch it offered on its Web site. It assessed the threat to computer users as “critical,” its highest rating.

A Microsoft security executive, Stephen Toulouse, said the flawed software was “an extremely deep and pervasive technology in Windows.” He urged customers to apply the patch immediately.

“This is one of the most serious Microsoft vulnerabilities ever released,” said Marc Maiffret of eEye Digital Security Inc. of Aliso Viejo, Calif., which discovered the flaws.

The disclosure comes just weeks before Microsoft Chairman Bill Gates delivers a speech in San Francisco at one of the industry’s most important security trade conferences.