After years of expensive litigation aimed at weakening its hold on the software market,

Microsoft

(MSFT) - Get Report

is on the verge of settling with nearly all of its opponents.

On Monday, the world's largest software vendor announced that it will pay $536 million to rival

Novell

(NOVL)

and reached a settlement with a coalition of high-tech companies that has sued Microsoft repeatedly.

The news gave a sharp boost to Novell; in recent trading, shares were up 68 cents, or 9.9%. Microsoft was off 4 cents to $29.27.

The agreements allow Microsoft to finally estimate its remaining legal exposure related to antitrust matters: $950 million, or up to 6 cents a share, according to Ragen Mackenzie analyst Jonathan S. Geurkink, who added in a note to clients, "We believe Microsoft's ability to quantify its remaining exposure is important since antitrust litigation has long been viewed as a nebulous and portentous threat."

Since Microsoft, whose Windows operating system dominates much of the software world, was declared a monopoly by the U.S., the Redmond, Wash., giant has spent about $3 billion to settle legal disputes with a long list of rivals and numerous class-action suits accusing it of overcharging consumers.

Microsoft and Novell were in private mediation over the impact of Microsoft's NT operating system on Novell's NetWare during the 1990s. Novell, which claimed that Microsoft drove its network operating system out of the market, will release Microsoft from antitrust claims in the U.S. and abroad, and withdraw as an intervener in the European Commission's antitrust proceeding against Microsoft. The EC case is under appeal.

"While we have agreed to withdraw from the EU case, we think our involvement there has been useful, as it has assisted the European proceedings and facilitated a favorable settlement with Microsoft," Novell said in a release. "With the EU case now on appeal, we are comfortable with our decision to withdraw from the proceeding. There is simply not much left for us to do."

Commenting on the Novell case, Microsoft Chief Counsel Brad Smith said: "Clearly, there is less need for the EU to persist with its lawsuit against Microsoft when virtually all of the competitors say their issues have been resolved to their satisfaction. We are prepared to sit down with anyone to find common ground."

In a subsequent conference call Monday, Microsoft said it has settled with four of the five major players involved in the EU case; only

RealNetworks

(RNWK) - Get Report

remains, although Microsoft wouldn't say if it was negotiating with RealNetworks toward a settlement.

Even so, Microsoft is still waiting to hear if the European Commission will reverse the earlier judgment against the company. In March, the commission said that Microsoft had abused its "near monopoly" power and levied a record $613 million fine, as well as ordering the company to ship a media-player-less version of its Windows operating system. It also ordered Microsoft to release a programming code that allows Windows computers to run better with other companies' servers.

A European Commission spokesperson told

Reuters

on Monday that its case against Microsoft will move "full speed ahead" despite the settlements. However, a new European competition commissioner will take office in a few weeks; that person will have power to reconsider action on the case,

Reuters

said.

The agreement with Novell follows a similar payout in April to

Sun Microsystems

(SUNW) - Get Report

over server software, and will reduce Microsoft's already reported first-quarter earnings.

Microsoft will expense an after-tax $359 million, or 3 cents a share, for the settlement, reducing its first-quarter earnings to $2.53 billion, or 23 cents a share. The company previously reported earnings of $2.9 billion, or 27 cents a share, in the quarter.

The Computer and Communications Industry Association, which has vigorously fought Microsoft on several legal fronts for more than a decade, also settled with the company, but it did not disclose the amount of its payment. It said Microsoft will spend $65,000 to become a member of the trade organization. Its members include many Microsoft rivals, including

Oracle

(ORCL) - Get Report

Sun Microsystems and

Red Hat

(RHAT)

.

In turn, CCIA agreed not to seek help from the U.S. Supreme Court review of Microsoft's settlement with the Department of Justice in its antitrust case and will no longer participate in the European Commission case. CCIA also will withdraw an EC complaint related to Microsoft's Windows XP operating system.

"Ten years of litigation is a long time to fight a company like Microsoft," Ed Black, the group's head and one of Microsoft's most vocal critics in Washington. In an interview with the

Associated Press

, Black said he will not recant any of his past criticisms of Microsoft.

One legal entanglement not addressed by Monday's settlement is a case Novell brought against Microsoft when it still owned the WordPerfect suite of word-processing software between 1994 and 1996. Novell said it would file a new antitrust suit related to those claims this week in federal court in Utah.

Novell will seek unspecified damages arising from Microsoft's alleged efforts to eliminate competition in the office applications market during the time that Novell owned the WordPerfect word-processing application and the Quattro Pro spreadsheet application. Novell said its suit will draw on the U.S. antitrust settlement with Microsoft, in which the company was found to have maintained a monopoly on operating systems by driving out competition in related markets.

Microsoft said Monday that it believed Novell's suit has no merit and has passed the statue of limitations.