Change Size Of Thumbnails

You can change the size and quality of the shell's thumbnails. Start regedit, expand HKEY_CURRENT_USER (only for you) or HKEY_LOCAL_MACHINE (for all the users in this computer) and in Software – Microsoft – Windows – CurrentVersion – Explorer, add or modify the following entries:

Thumbnail Size – Double Word, decimal value between 32 and 256

Thumbnail Quality – Double Word, decimal value between 50 and 100