I'm just learning RTOS myself, when i execute the bl51.exe from a command line c:\keil\c51\bin\bl51 task0.obj, rtx51tiny as i found it in keil rtx51 tiny User's Guide , the following error occured. ***FATAL ERROR L210: I/O ERROR ON INPUT FILE EXCEPTION 0021H: PATH OR FILE NOT FOUND FILE: RTX51TINY what should i do to overcome the error?????