Thank for the answer.

What I meant by "growing" is that the file pass from 900K to 2.2 Mg. Maybe it is a wrong word for saying that the file is larger than before and for no reason we know. You said that windows bundle VxD together so it answers my question. Thanks.

Another question:

Is it possible for a programmer to call function in those VxD file. If yes How? (just for curiosity)