SoV i needz ure H31p

I think you'd need to use D2 Loader.

C3PO has an option to load d2 in windowed mode as well.

you right click on your d2 shortcut on your desktop, Select properties, find the line that says Target, at the very end of that line, add -w (put a space after the last character before you add -w).

Ex: "C:\Program Files\Diablo II\Diablo II.exe" -w

on a side note, you can add other targets to mess around with.

-ns causes d2 to have no sound so you can listen to music
-skiptobnet lets you skip right into the battle.net log in screen.

theres more, i can link you later if you want.

d2loaer+ windowed mode fixed 99% of my lag problems