Details
When you have set the Windows Explorer to thumbnail preview and activated the "show thumbnail icons" for the folder options and you still don't see any NX part previews (or when you have installed NX 12 you might only see the thumbnails up to NX 11parts).
Solution
The reason for this might be a wrong registered NX DLL which controls the thumbnail preview within the Windows Explorer. The DLL in this case is the ugshext.dll, located in the UGII (or NXBIN) folder underneath your NX 12 installation.
Starting with NX 12 the way the thumbnail image is embedded within the part file has changed. So if there is the DLL from a previous NX release registered within Windows and available due to an older installation of NX on the system you only can see the images of parts up to NX 11.
To get the thumbnail preview working correct you need to register the correct (NX 12 or later) ugshext.dll with Windows.
This is an example of the command to be used in a command prompt to do this:
regsvr32 -u "c:\SIEMENS\nx10\UGII\ugshext.dll"
regsvr32 "c:\SIEMENS\nx12\NXBIN\ugshext.dll"
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: 1064
Product: NX
Application: SYSTEM
Function: WNT_OS_ISSUES
Ref: 002-8008019