Dear Peter, I am using olr160330.tgz Browser.Showdef not working. Compiling Browser.Mod says Modules.extension not defined. Compiling Modules.Mod says new symbol file includes extension now. But Not able to reload Modules. :-( It says reference count not zero. System.State on Modules says importing = Modules, imported = Modules. Something little absurd. True that Modules can't be unloaded. Can we? Can we unload Kernel too? System.State's output also seems little confusing. Anyway, I thought, if Modules can't be unloaded at runtime, no issues. I have already compiled Browser and Modules along with new symbol files. So a System.Reboot will do the job. Excellent. It did half the job! Earlier Browser.ShowDef was generating a TRAP. Now with new Modules loaded, it says Browser imports incompatible version of Modules. extension incompatible. Now, how to proceed? With thanks and best regards, Yours sincerely, Srinivas Nayak Home: http://www.mathmeth.com/sn/ Blog: http://srinivas-nayak.blogspot.in/