The 39-year-old Texan, identified only as John S., was convicted on three counts of counterfeiting patent-protected programs and smuggling them in to Germany for commercial purposes.

Microsoft welcomed the court's decision as "a meaningful signal" to those engaged in computer piracy.

The software giant said the case - involving $63.8m worth of counterfeit programs - was its biggest in terms of the sophistication of the operation and the magnitude of damage.

Speaking after the sentence was passed, Rudolf Gallist of Microsoft said: "This sentence is a breakthrough in Germany and shows that counterfeiting software is really a serious crime."

The court refused Microsoft's request for damages, saying that should be handled by a court in the UK, where the counterfeiters allegedly ran their production plant and printing operation.

The Texan is also facing charges in England.

The case against him was the result of a German customs office investigation last August which uncovered some 300,000 counterfeit CD Roms, featuring programmes like MS Office, Windows 95, and Windows NT, along with faked certificates of authenticity and 400,000 installation handbooks.

The fakes, which had been smuggled into Germany, were found in a rented container and a warehouse in the town of Kreuzau, about 30 kilometers west of Aachen.