The bidding war for Quest Software Inc. is on, and New York-based Insight Ventures Partners has regained the lead.

The New York-based private equity firm on Monday topped a Friday offer of $2.15 billion by a strategic buyer, according to a Bloomberg report citing an unnamed source.

Friday’s bidder was widely believed to be Dell Inc., the world’s third largest computer maker.

That takeover offer topped a proposed $2 billion deal led by Insight Venture.

The company had the right to match competing offers within three business days, under its original deal.

Company watchers and industry sources have linked Round Rock, Texas-based Dell with Quest since the company announced in early March it was slated to go private.

Investors sent Quest shares up 1.6% in extended trading Monday on word that Insight took the inside rail in its bid to acquire the Aliso Viejo software maker.

Quest makes software that manages and improves on other business products from Redmond, Wash.-based Microsoft Corp., IBM Corp. of New York and Redwood Shores-based Oracle Corp., other potential suitors linked to the company.

Quest is one of Orange County’s biggest software makers with $857 million in sales in 2011. It has 3,000 workers overall, about 600 here.

The pact with Insight Ventures includes a relatively small break-up fee of $6.3 million if a deal is not reached.

The strategic bidder would pay Quest a break-up fee of $75.2 million if a deal is terminated under “certain circumstances” or $43 million if the acquisition is not approved by shareholders.