I tried it in XP but it didn't overwrite the registry like it should have.
Thanks to Blahman in this thread, we have a fix for this issue. I will post the exact instructions later (it's a little complicated), but basically you need to use OverrideEdidFlags0 with an EDID modified so that number of extensions is 0 rather than 1. This seems to disable the monitor advertising itself as an HDTV.