Hi,
Welcome to JavaRanch!
No, you don't have to give the full path, but your PATH environment variable needs to point to the directory in which WINWORD.EXE resides. In general, if you can bring up a CMD window and type WINWORD.EXE and have
Word launched, then Runtime.exec() would work without the full path -- but it CMD can't do it,
Java can't, either.
This is not an advanced Java programming question, so I'm going to slide this over to our intermediate forum.