What is Thumbs.db

Thumbs.db is a cache file that is used by Windows in any folder it finds a picture or video. It is intended to speed up the displaying of thumbnails. Windows Explorer uses thumbs.db to view cache images when the folder is viewed in Thumbnails view. The thumbnails are created and saved once as thumbs.db instead of creating thumbnails 'on the fly' each time Windows Explorer displays the contents of a folder. Thumbs.db stores data for the following formats: JPEG, BMP, GIF, PNG, TIFF, AVI, PDF, PPTX, DOCX, HTML etc. Thumbs.db is a hidden file. It means that you could see it in windows file manager only if you checked 'Show hidden files and folders' in Folder Options. 

In Windows Vista and Windows 7, a central cache of thumbnail images was invented. The thumbcache is stored at %userprofile%AppDataLocalMicrosoftWindowsExplorer as a number of files with the name thumbcache_xxx.db where xxx is a number between 1 and 999.

Thumbs.db is totally safe to delete. It will be automatically generated next time you browse a folder in Thumbnails view. But you could disable re-creation of it. In Explorer, go to Tools, then Folder Options and click on the View tab. Check the box “Do not cache thumbnails” and click OK. You can also change this setting in the Registry. Open the Registry Editor (regedit.exe). Go to HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerAdvanced. Double-click the DisableThumbnailCache value, or go to Edit -> New -> DWORD value to create a new value by that name. Enter 1 for its value. Click Ok and close the Registry Editor when you're done; you'll have to log off and then log back on for this to take effect.

Note: Any malware can be named anything - so you should check where the files of the running processes are located on your disk. If a "non-Microsoft" .exe file is located in the C:Windows or C:WindowsSystem32 folder, then there is a high risk for a virus, spyware, trojan or worm infection!