My virusscan detects viruses in Rayman 2. I've found similar reports here for Rayman 1 but not for Rayman 2. Is this a false alarm? My anti-virus-software is GData and my system Windows 7.

It is most likely a false alarm, caused by virus scanners assuming the code of Rayman 2 is malicious. Back in the day when it was released, it wouldn't have been used maliciously, but hackers are now using similar code in a way to harm others, hence the virus DB's now flag anything using similar code as a "virus". Just ignore, add to exclusions etc.