FLORENCE, Italy, Jan 5 (Reuters) - An Italian consumer group is planning a class-action lawsuit against Microsoft Corp MSFT.O seeking compensation for Windows software pre-installed on computers for people who did not want it.

The Aduc consumer defence association said on Tuesday it would present its case at a court in Florence after Wednesday’s Epiphany holiday.

The move against Microsoft, the world’s biggest software company, comes after a law took effect on Friday allowing consumer associations to file suit for groups of consumers.

“Individual cases affect a limited number of users,” Aduc Chairman Vincenzo Donvito told Reuters.

“Therefore, as there is a large number of users involved, and with the importance of the free market issue, we have decided to take a collective legal action against Microsoft.”

Italian law provides for compensation for costs and not punitive damages. Microsoft was not available to comment.

Aduc has won a pilot case in a Florence court on reimbursement of the cost of Windows for consumers who had to buy it pre-installed on computers. (Reporting by Silvia Ognibene and by Sara Rossi in Milan, writing by Marie-Louise Gumuchian, editing by Will Waterman)