The error message means javadoc cannot find the source file. When passing in source files, you must specify the relative or absolute path to them. You didn't say what your current directory is. This should work:
cd "c:\program files\java\bin"
javadoc -d docs diceGame.java
Then point your browser to c:\program files\java\bin\docs\index.html
I strongly recommend using the -d option (destination) to create a directory in which all the HTML files go, so they don't get scattered in your bin directory.
You probably don't want the -package option, as that documents all package-private members.
-Doug