afaik, there is no way to prevent the creation of msoecache folder in office 2007. i've run into issues uninstalling it after deleting that folder (and freeing those 530mbs of space). but then mebbe the problem is restricted to me as i was using the trial version and the trial period got over. i don't haf full version. so mebbe someone else can confirm. but what i'd like to point out is that i've run into problems while uninstalling it after removing that folder.