I heard that I could have diablo play on a desktop window. Can someone explain to me how to do that?

you have to go into the shortcut that runs the game and add /w to the end of it and it should work

I have tried adding /w to the end of it. Either I am attempting to add it in the wrong place or it won't work. Can you specify where exactly I need to add /w?

Start the game with the -w command line parameter to run it on a window on the desktop. To do this, right click the icon and select "Properties" at the bottom of the list. Next, where it states "Target:" go to the very end and add -w (outside the quotes). When you double click this specific icon, it will open in a 800 x 600 window size. When you play the game itself, it runs under the 640 x 480 size, unless you specify otherwise with the newer patches.

Tried it it says:

"The name "C:\Program Files\Diablo II\Diablo II.exe"-w specified in the Target Box is not valid. Make sure the path and file name are correct.

the shortcut should look like this
C:\Program Files\DiabloII\DiabloII.exe-w
notice how the -w is at the end computer don't do so well with just blank spaces.