What are the usual fixes for the error message:

A critical error has occurred while initializing direct3d

when starting up D2?
Im on a mac, attempting to run diablo on windows 7 through a virtualbox.
Please redirect me to the correct forum if this isnt a place for this.

You may get more detailed advice from users here: Computer Hardware and Driver Help
Be sure that you have the necessary drivers that correspond to your graphics card to support DirectX.
(Though I'm not too sure how it works with virtual OS systems, I've never used one, nor had any reason to)

You have to re install your "Diablo II" client JetFan2010 to fix the Direct3D error. Good luck.

You know, in all my frantic efforts to find the right directx versions and drivers, i've totally overlooked the simple fix of reinstalling.
I'll try it out, thanks for helping.

d2 apparently has issues with win 7 so if you can get an older version of windows you shouldn't have a problem

also why not just run it on your mac? there is no need for a virtual box or anything like that

Either try out the Mac version of Diablo 2 or make sure all necessary drivers are up to date. If you need help with the latter case, do the following:
Go to Start Run dxdiag

On the first tab (system), post this:
DirectX Version

On the second tab (display), post these:
Device Name
Driver Version & Date

we are not allowed to discuss it?

since it ain't allowed to run 2 diablo on 1 pc

DirectX Version: DirectX 11

Device Name: Standard VGA Graphics Adapter
Driver Version and Date: 6.1.7600.16385 7/13/2009, 5:38:47 PM

I have a funny feeling you don't know what a virtual box is.

Seems like dxdiag can't identify your graphic card correctly. Please download Everest Ultimate and check your graphic card again.

Outdated drivers are the last thing I could image of being the cause of your issue, since no other Solution I know of solved it.