Some time last months all the Thumbnails in Explorer disappeared for me. It might have coincided with me installing VLC Player on Vista. Either way, it sucked because I had family photos with thumbnails next to videos taken with the same camera with no thumbnails. It's no fun to lose functionality.
While poking around in the Registry trying to fix this issue, I noticed that Thumbnails for AVI files worked, while no others did. The only difference with that extension was this registry key:
So, I made a registry file with this entry for each extension I wanted thumbnails for. Merged it into the registry and, lo and behold, I have thumbnails again. The file is below.
As an aside, while I was trying to fix this, I also picked up a codec pack called the CCCP (Combined Community Codec Pack) and noticed while running through its settings that it had an option to "fix perceived types." I wish I'd known this last week when I fixed THAT problem with missing Media Center Thumbnails.
Switching over to the CCCP also had the added benefit of letting me watch my MP4 encoded PSP (Playstation Portable) files in Windows Media Player, and added Thumbnails in Explorer for MP4s as well via their settings dialog. Once I got MP4 working I exported those settings and appended to them to this file.
Also, by the way, did you know that the new location of the Explorer Thumbnail Cache is down here?
Volume in drive C is 70 GIGS SYSTEM
Volume Serial Number is 98A2-64B2
Directory of C:\Users\Scott\AppData\Local\Microsoft\Windows\Explorer
04/18/2007 10:29 PM <DIR> .
04/18/2007 10:29 PM <DIR> ..
04/18/2007 10:29 PM <DIR> ThumbCacheToDelete
04/18/2007 10:29 PM 24 thumbcache_1024.db
04/18/2007 10:29 PM 1,048,576 thumbcache_256.db
04/18/2007 10:29 PM 24 thumbcache_32.db
04/18/2007 10:29 PM 1,048,576 thumbcache_96.db
04/18/2007 10:29 PM 4,064 thumbcache_idx.db
04/18/2007 10:29 PM 24 thumbcache_sr.db
6 File(s) 2,101,288 bytes
3 Dir(s) 21,871,742,976 bytes free
Crazy new stuff this Vista, eh?
No warranty or support, express or implied. YMMV. Backup your Registry before you do this and please don't come to me if your world is destroyed. You have been warned.