I have the same problem and I have a simple trick that should work.
Windows Vista won't show MOV, QuickTime or Apple type video thumbnails like Windows Media Player. What I do is I go to a site where I can actually download one of these aforementioned video files (i.e., MOV, QuickTime) and act like I am going to download the file.
- Right-click on the link or file
- Select Save Target As when the Save As dialog box opens
- Navigate or browse over to the very exact folder where you have those MOV or QuickTime files that won't preview.
If the file that you are pretending to save is similar to those, you will readily see your files. If you don't do anything, after about 10-15 seconds the thumbnails will begin to auto-populate in the dialog box.
If you do not see your thumbnails in the dialog box then that means the file you are saving is somewhat different from the files that you have.
What you have to do then is just look at the bottom of the dialog box where it says "File Name:" and "Save As Type:" and click the "Save As Type" and select All Files and BOOM, your thumbnails will suddenly appear. Of course you still have to wait the 10-15 seconds for the thumbnail previews to start auto-populating.
Once they start to auto-populate, it generally takes 15-30 seconds for each thumbnail to generate a preview.
You can speed up this process by selecting View from the menu and changing it to the smallest viewable icon, probably Medium.
They will then load faster. If it stalls, right-click in an empty part of the screen and refresh the screen and they pop up faster.
Do not have the folder with those thumbnails open at the same time. Sometimes it makes it take longer. If you have it open have it minimized and after all thumbnail previews load, then open it up and click refresh and there you have it.
There is only one little problem with this trick!
I don't know this for a fact but I will almost bet you all of Memo Porton's and Esteban Trabajos career-monetary take from MS and Apple RESPECTIVELY that when you do it this way those thumbnail previews of yours (ours, everyone's) are somehow sent, directed, shared, transported, communicated, forwarded or whatever to their respective companies so that they can get a sneak peek on what people in this world are recording.
Remember all that jive about how they retain the right to do whatnot as long as there is no personal identifiable information or some jargon in all of their agreements that you have to accept?
Well, there it is.
So, even though you think your previews will get lost somehow in the millions or billions of thumbnails or that they will magically be erased, they will not be. Nothing is ever dispensed with, ever!