Win7 thumbnails can't be displayed? Experts help you get it

My Win7 Ultimate, the player is KMPlayer. A few days ago, I installed RealPlayerSP and felt it was not easy to use. Then I deleted it. Later I found that I could not see the real-format streaming media file on the webpage, so I reinstalled the real alternative, win7codes and other decoding packages. Now I have no video playback. The problem, but those files in AVI, WMV, MPG format can not display thumbnails, but VOB, mkv and other formats without thumbnails can look at the thumbnails. I have tried countless methods, I think it is not a common problem, so ask Master? Is there any solution to this problem? In fact, this problem is not a problem with a certain hardware. Below we will make a comprehensive answer based on this question.
1, immediately check the remaining space of the C disk
If only a few hundred or tens of megabytes, please clean up the useless files of the C drive or transfer the useful files to other disks. This way the thumbnails will display properly. It is recommended that the system disk keep the remaining space of the disk twice the size of the memory.
2, open a folder with images, right-click "View", change the view mode.
If it is normal to display thumbnails in small icons, lists, or detailed information, use other viewing methods to display them.
3. Double-click "computer"
find the "folder and search option" in the "Organization" drop-down menu, and find the "always icon in the "View" option. Never remove the checkmark before the thumbnail " option, then click OK.

4. Right-click "Computer" Click "Properties"
Select "Advanced System Settings", then click Performance "Settings" in the "Advanced" tab. , check "Show thumbnails instead of icon "options, click OK.
5. Rebuild Thumbnail Cache
Type "Disk Cleanup" in "Start Search Bar", then press Enter to open the Disk Cleanup Tool and select the system drive letter (eg C:) , click OK, pop up the dialog box computer time does not need to hang, then just select "thumbnail", click OK, confirm in the pop-up box "delete file".
clear the icon cache, then open the file The thumbnail should be back to normal.