[andrewas]

If youve lost all the registry keys, you can safely remove the files. Make a copy of the save game folder before you do it.

Then, just re-install and your sorted.

You might even be able to get away with just installing the game over the top of the old installation.

If you have only lost part of the registry keys, then something weird has happened. But its fixable, just go into regedit and *carefuly* remove all keys related to baldurs gate and interplay.