Hello,
In Windows, a file can be named A&B.ext. Lazarus refuses to accept a project name which contains an ampersand which is valid in Windows.
Hardly a big deal but, I thought it was worth mentioning since the ampersand is a valid character in a Windows file name.
For the record, the compiler doesn't mind the ampersand in the file name. It compiles it as it compiles any other file.
NOTE: the ampersand is the only character that I know of so far that causes the problem but, its presence suggests there may be others.