A US judge has given the final approval to the $1.1 billion settlement reached between the state of California and Microsoft over its anti-trust activities.

The class-action lawsuit accused Microsoft of overcharging California consumers, schools, and businesses for Windows and other products. It was launched in 1999 and settled in January 2003 - a month before it was due to go to court.

The massive $1.1 billion settlement is the largest ever achieved under anti-trust laws, according to the law firm that ran it. And in his 31-page order, California Superior Court Judge Paul H. Alvarado said it "constitutes fair, reasonable and adequate compensation."

Microsoft must now distribute varying vouchers for purchasers of its software which can be redeemed for software or some hardware from a variety of manufacturers. Californian citizens will receive a $16 voucher for each Microsoft Windows or MS-DOS software license; $29 for Microsoft Office; $5 for Word, Home Essentials or Works Suite; and $26 for Excel.

It amounts to 14 million eligible applicants, 600,000 of whom have already registered. More information on applying for the vouchers is on a dedicated website at microsoftcalsettlement.com.

The final approval comes a week after Microsoft also settled with Arizona and Massachusetts and saw a Federal appeal against it rejected.

Microsoft has now settled 13 state class actions(Arizona, California, Florida, Kansas, Massachusetts, Minnesota, Montana, North Carolina, North Dakota, South Dakota, Tennessee, Washington DC and West Virginia). Still outstanding are lawsuits in New Mexico, Iowa, Nebraska and Vermont. Appeals against declined lawsuits are ongoing in New York, Ohio, Wisconsin and Michigan.