I eventually got some work done this week, but still not quite there. The problems regarding the reported file size was easily fixed, once I saw the error. It was a rather embarassing error. Apparantely the Java type "long" was defined as a 32 bit value, where Java wants a 64 bit type. Easily fixed, and kind of in the areas of what I thought was wrong. Following that fix, my current problem arise around opening file through the Java URL class, i.e. on the "file://SYS:s/startup-sequence"-form. I had the feeling this would come and bite me, sooner or later. GNU Classpath supports Unix and Windows paths, and it decides which system is in use by checking the file separator; if its backslash, its Windows, if it isn't we have Unix. A very pragmatic look, but not terribly allowing for other systems. I'm currently going through the Java class hierarchy to try and find where exactly it doesn't work, because in some cases it works, and in other cases JamVM is trying to reach volumes named "/SYS:".