mount d d:\ -t cdrom
see the readme

What do you mean with this?
How does it help?

Mounting something as CD-ROM drive enables mscdex inside DOSBox.

Ok.
I have now an other problem.

MSCDEX works but the program says that i have the wrong cd inside.
But I defined the path where the cd files are inside as the cdrom.

what is now wrong?

What's the drive letter of your cdrom?
If it's say E: then try
"mount d e:\ -t cdrom -ioctl"
maybe adding usecd as parameter, too (examples are in the readme)

And maybe you need to supply a valid label as well.

E.G.

mount d e:\ -t cdrom -usecd 0 -ioctl -label MYDISK