I often have problem to delete a folder that contains a thumbs.db file. Also tools like "unlocker" fail. It seems to be loccked by os for some unknown reason. The only solution i found in the net was to disabling thumbnails in windows but this is a bad workaround isn't it?
Is there a "normal"(or official, supported by MS) way to delete an empty folder that only contains a thumbs.db?
It is circuitous but I don't know why disabling thumbnails, deleting the folder and re-enabling thumbnails is "bad". Anyway if you don't want to do it then a simple logoff and logon should close any open file handles and allow you to delete the folder.
Alternately you can also try to delete it after closing Explorer (by Ctrl+Shift+clicking an empty area of the Start Menu for example) and then restarting it from Task Manager (Ctrl+Shift+Esc > File > New Task > Type explorer > Enter).
I think if the deleted item is still in the trash, the thumbs.db file will stay in use in the original folder. Try emptying the trash, then deleting the thumbs.db file. It worked for me.
in meanwhile i found acceptable solution: disable "display file icons on thumbnails" in folder's view options. i think this is the cause the explorer holds an handler on thumbs.db. The problem with this is you have to re-enable this if you want.