Background Programs
If your system has several programs running constantly in the background, these can interfere with the smooth operation of Diablo II. Press the "Ctrl," "Alt" and "Del" keys at the same time to bring up the Task Manager. End all programs except for Explorer and Systray. When your computer restarts, any background programs you previously terminated will be running again. If you want to alter your startup programs, click the Windows orb and type "msconfig" into the search box. Press "Enter" and click the "Startup" tab. Remove the check marks from all the boxes and click "OK."
Game Patch
Blizzard routinely releases minor updates and fixes to its stable of games. These updates, called patches, ensure that known errors are corrected and you enjoy the smoothest possible gaming experience. The most recent update for "Diablo II" is 1.13d. Players whose games aren't fully updated may suffer from crashes and lockups, including "unhandled exception" errors. Blizzard's support pages include download links for the latest patches to all of its games.
Reinstall
A glitch during the installation process may introduce errors that only appear later during gameplay. "Diablo II" is a large game, and installation makes heavy demands on your system. If your game has the latest patch and you still experience errors, try completely uninstalling and then reinstalling the game. Make sure that no other applications are absorbing your computer's resources during installation. After the game has been installed, go to Blizzard's support site and download the patch. Run the game and see if the "unhandled exception" error returns.
Device Drivers and DirectX
Outdated drivers for your video or sound cards may lead to sub-par gaming performance. Windows Update won't necessarily keep track of these drivers, especially if you install third-party, aftermarket hardware such as a high-end video card. Type "dxdiag" into the Start menu seaech box and click "OK." Click the "Display" tab and scan the information for your video device, including manufacturer and driver. Visit the manufacturers' websites to determine the latest driver version. Download and install these newer drivers as necessary.