I can't see image previews on Windows 7. Only icon view on all pics. Other computers work fine. I checked the pic views
Thumbnail display in Windows Explorer relies on two things, an appropriate Windows Imaging Components (WIC) Codec and having the option to display thumbnails enabled in windows explorer. It is enabled by default.
It's most likely that you don't have the codec installed. It can be downloaded from the Microsoft download centre.
Microsoft Camera Codec Pack
This has both 32 and 64 bit support and is automatically updated to support new cameras from a range of manufacturers. Now that Microsoft have released a pack, most manufacturers have stopped updating their own codecs. Nikon was the only manufacturer who appears to be making updates publically available when I looked.