[andrewas]

The site I normaly get this kind of info from is down, which makes thins tricky. But I ran across this from the IWD tech FAQ

Q: ILLEGAL OPERATION DURING INSTALL: During the installation of Icewind Dale, I receive an Illegal Operation crash in the installation, sometimes saying something about ZDATAI51.DLL. What can I do? A: This error appears to be caused by bad disc media. Check the bottom of the disc for scratches, dust, dirt, or fingerprints. If any are found, try cleaning the bottom of the disc with a lint-free cloth. If the crash continues to occur even after cleaning the disc, return the game to your retailer for another copy. Some further information: This problem was sent to InstallShield, and their technical support also recommended several other things to try: Disable any antivirus programs that are currently running, delete the contents of your Temp directory (usually C:\Temp or C:\Windows\Temp), or try installing in Safe Mode.