I got my thumbnails visual by using 32-bit explorerer on a 64-bit machine (Vista). But all of a sudden this doesn't work anymore. Could this be caused by an update of Microsoft or Adobe? ('pretentious' didn't work for me but maybe that's because I didn't cleared my thumbnail cache)
I'd been working fine for a while, but then a few months ago again lost the preview functionality. I'm running 64-bit Windows 7 with Office 2010, and Adobe Reader X. I checked the registry, and that's OK, tried repairing Reader & Office, all to no avail. Finally, I uninstalled and reinstalled Reader and now all is well again! Go figure; I haven't had to go the "reload" route in a while I suppose an update/fix install doesn't go through the whole process necessary to configure the previewer.