This might be the wrong group for this but .vstudio.development have low activity and if the problem is a vstudio bug users of this group probably have run in to it. Anyway, i have recently set up a development environment on 64-bit Vista and run into this problem. The debugger cannot display the value of GUIDs, they are all displayed as {????????-????-????-????-????????????} ( In call to eg. IFolderView::Items() ) Have anyone else run into this problem? Is there any settings that can be tweaked to remedy this problem? My env. is Vista x64, devstudio 2005 with SP1 and the vista SP1 update. It would also be intersting to know if anyone with the same config can display GUIDs in the watch window. Regards Magnus