I can open them in browser just OK, but how can I have thumbnails in the Windows Explorer?
Edit: I installed Renesis Player as suggested by this answer, but it does not work for me, probably because I have 64-bit system.
Use this awesome SVG thumbnail shell extension which works fine in Windows 7 & Windows 8 (both 64-bit and 32-bit):
It is open source and free - what can you ask more?
If you still have problems to view the thumbnails after installing this shell extension please refer to these instructions how to reset your icon cache in Windows 7/8.
This works on Windows 8.1 Pro 64-bit.
In regards to the answer given by geo, in the event someone needs to rebuild the IconCache.db and wants to give a go at not needing to reboot try the following batch.
Adobe Illustrator isn't the only way to do this, nor is it the best way to do this.
See the post by @Deckard above...
Follow the link he provided to the SVG Explorer Extension. Download and install Dotz Software SVG Explorer Extension, aka DSSEE.
Once installed, open Task Manager and kill all instances of explorer.exe. From the Task Manager menu, choose File->Run new task menu. In the dialog box, simply type explorer and hit OK.
NOTE: Please do the above step only if you're comfortable with killing and restarting processes through the Task Manager. If not, then simply reboot your system so that the new explorer extension can load.
From then on, all SVG images will show up as thumbnails in Windows Explorer.
This extension has worked perfectly for me on both Win7_x64 and Win8_x64! In fact, I was recently pleasantly surprised to learn that it displays thumbnails for compressed SVGZ images as seamlessly as it does the non-compressed versions.
Per the comment by John Rasch, if you can't see the SVG thumbnails after following the steps above, you can clear your icon cache using the following batch file:
Copy this to RebuildIconCache.bat and run it as Administrator. It will kill all Windows Explorer processes, which is required before you can delete the icon cache, then delete the icon cache, and, finally, reboot your system.
I know this question was asked about Windows 7, but I thought it would be useful to add instructions for Windows 8 and above...
Windows 8 introduced a new icon and thumbnail cache system. Instead of a single file containing the entire icon cache, Windows 8 uses multiple cache files, based on the size and type of icon. These files are stored in "%LOCALAPPDATA%\Microsoft\Windows\Explorer". As an example, that directory on my system includes the following files:
As a result, in order to clear the icon cache in Windows 8 or above, you would need to delete all of the 'iconcache_*.db' files in the above directory.
Note that, in addition to the above files, Windows 8 still retails the "%LOCALAPPDATA%\IconCache.db" file. I honestly don't know if this file is used or not, but, to be thorough, it would be best to continue to delete that file as well.
Therefore, for Windows 8 and above, we have the RebuildIconCache8.bat file as follows:
or as @user1698811 suggested:
which resets the icon cache without having to reboot.
If you are using Windows 7 64bit, you have only one way to see thumbnails:
Open (install) Adobe Illustrator trial, then press File > Open and change to a thumbnail view of your SVG files, and it will show all your SVGs.