akmsr,
You need to add a path. Find the directory where the java compiler is and add this to your autoexec.bat:
PATH C:\Java\bin\
where
C:\Java\bin\ is the directory where your java compiler is. That way you can the run the java compiler from any directory, not just the directory where the compiler is. Now just type
java filename
in any directory and it should work (as long as
filename exists in that directory). Also, you may want to use a text editor more powerful than notepad. I recommend
EditPad Lite. It's free and easy to use and it lets you open more than one file at a time (using tabs).
Hope that helps.