After reading
http://www.lazarus.freepascal.org/index.php/topic,11381.msg57164.html#msg57164
I am not experienced enough with the build process, and don't want to make it worse by "fixing" it wrong....
If anyone with experience may wish to take a look:
You will need a compiler to build a new compiler. Get the ppc386 (the compiler) in FTP (below) and unzip it in c:\freepascal\binutils\ ftp://ftp.freepascal.org/pub/fpc/dist/2.4.0/bootstrap/ppc386-win32.zip
I thought you need 2.42 to build 2.5.1 ?
and
In a console, cd into the bin directory, e.g. C:\freepascal\fpc\2.5.0\bin\i386-win32. Enter: fpcmkcfg -d basepath=C:\freepascal\fpc\2.5.0\bin\i386-win32 -o fpc.cfg
afaik there is no 2.5.0