Adobe used to install their own .dll to show thumbnails in Explorer but it caused some huge major problem that I no longer remember. They eventually stopped providing it and included Bridge instead.
Bridge is awful, IMO, except that it shows me whether I've made adjustments to camera raw files.
i dislike bridge too, that's why i was so pleased to find mystic thumbs.
i've installed on all my pc's and laptops and now it's just a matter of opening explorer and seeing .psd's just like jpgs. (unfortunately it wont work in pic/fax viewer, but then again, that wasn't my original gripe....