Install error: Invalid destination path! Try again.

[Hazardious]

I have Transport Tycoon Deluxe on CD, and I wanted to play it again under Win 7.
But I needed DOS to install it, so I downloaded DosBox 0.74.
When I mounted the CD Drive, and typed in "INSTALL", the main menu pops up.
But when I click install I get this error message all the time! I tried even different locations but it doesn't work.

Does someone have solutions?