Open your Windows Registry
*Regedit
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
. New DWord Value
. Name it “ThumbnailSize”
. Double Click it
. Enter value 256 for Decimal
. Close out your Windows Explorer – reopen
. You may have to delete your current thumbnail file.
Additional help links:
*http://www.online-tech-tips.com/windows-xp/how-to-increase-windows-explorer-default-thumbnail-size-for-pictures/
*http://teamtutorials.com/windows-tutorials/changing-thumbnail-size-in-windows-xp