A shadow copy? I thought Vista implemented the file redirection via symbolic links, if they have that feature in the SO, why create a new copy for every file a program create in its own directory? For antivirus software, that could be a nightmare, but I suppose Vista editions of those apps will do things right.
EDIT: After reading some things about the capabilities of Windows Vista filesystem, I have found out that there is no way to use folder junctions for files, the only way to implement what I thought I was talking about up here. So forget about the first paragraph, as I believed that symbolic links was a completely different thing that, as I say, does not exist. Basically, Microsoft made a mess IMO with the new possibilities they introduced for Vista filesystem, have a look
here for more information. You have everything, including the kitchen sink, but not the essential feature that would made file redirection work as it should, that is, file junctions.