I know this thread is almost a month old but it's if the original topic creator comes back and sees this or someone googles this problem and sees this. This is a problem with Windows Vista/7, here's the fix:
1) Create a shortcut to Starcraft and put it on your desktop
2) Right click on the shortcut and click Properties
3) In the Target box after the last quotation marks, add this: "ddemulate" with the quotation marks
4) Click Apply and close
5) Run Starcraft and enjoy your fix
Your box should look like this:
C:\Program Files (x86)\StarCraft\StarCraft.exe "ddemulate" Change it to wherever your Starcraft directory is in as well
xboi209@yahoo.com -email me if you need tech support
Sorry but I no longer offer tech support for Diablo and Diablo 2 because I know the answer to your question already, THERE IS NO COW LEVEL!!!