Photo Gallery does have a setting that will clear the original images after a certain number of days - for me it was set as 1 day by default.

Huh, nifty. I never thought to check whether there was an option associated with this. Mine was set to “Never” by default though.

Thanks so much for this! I found hundreds of old images in that folder! I was going crazy trying to figure out how Vista remembered all the changes I made to photos.

If you didn’t even know those photos were there, you might benefit from deleting them all and clearing up the space. Glad this tip helped!