Charges have been dropped against a Russian school headmaster who faced up to five years in prison for software piracy, according to Russia's state news agency.

Alexander Ponosov, 40, was charged with violating Russia's copyright law after police seized 12 computers from his school in the western Russian village of Vereschagino.

Police say the PCs contained more than $10,000 in pirated Microsoft software, but Ponosov claims he bought the computers with the software preinstalled and has maintained his innocence.

The case drew international attention last week when former Soviet Union president Mikhail Gorbachev wrote to Microsoft chairman Bill Gates asking him to intervene in the matter.

Gorbachev wrote that while Russian law allows for the prosecution of those who unknowingly use pirated software, the case against Ponosov is unwarranted. The former leader also made an emotional appeal, writing that Ponosov dedicated his life to teaching for a modest salary, which doesn't compare to those of Microsoft employees.

Gorbachev's high-level intervention has come as Microsoft pursues an aggressive legal campaign to stop piracy of its software. Microsoft has launched dozens of civil lawsuits and aided law enforcement in criminal investigations throughout Europe and the US.

The charges were dropped Thursday for lack of evidence by a regional Russian court, according to RIA (Russian Information Agency) Novosti, a state news agency. If convicted, Ponosov would have faced a fine of up to 266,000 rubles (£5,200) in addition to a possible prison term.

State prosecutors are quoted as saying they may appeal the decision within 10 days, according to the report.

Microsoft officials could not be reached immediately for comment.

Jeremy Kirk contributed to this report.