OH heres something a might as well ask.
did you buy the LOD CD from a place like gamestop to replace your original?
I did this with my starcraft brood war (my original was on one disk and it was to scratched), but the replacement one (looked exactly the same the mine) but required a second disk because it was an older version
if that's the case then you might as well just buy a new Diablo battlechest somwhere