< snip >
>In the old DOS days we used to append stuff to the .exe using low level file functions. The trick is to find the end of file marker, remove it, insert a binary value and a new end of file marker. Mostly this was used to insert user IDs on setup. It was risky in DOS if you were not very careful.
>
>I have never tried this with a Windows .exe, so I have absolutely no idea if it would cause problems.

Most of your virus checkers would blow the whistle on this kind of activity...