Windows Vista was released a couple of days ago, some of you might be upgrading. So, you may realise that Diablo 2 will not run by default. Here's how to get around this.
1.) Go into c:\program files\diablo II\ or wherever you have the game installed.
2.) Right click on "game.exe" and go to properties.
3.) Click on "Compatibility" tab
4.) Place a check in the box that says "Disable Desktop Composition"
5.) Click Apply. Click Ok.
6.) Run the game! It should load and play normally once this option is checked.