Pictures and Backgrounds in Windows
From Free Knowledge Base- The DUCK Project: information for everyone
User Account Picture
Your user account picture on the Windows login screen is part of a set provided with the operating system These are 16 million color bitmaps. The profile picture size depends on your version of windows. You can select one from the defaults provided or create and use your own.
Windows XP
These pictures are 48x48 24 bit. The path to the default account pictures:
C:\Documents and Settings\All Users\Application Data\Microsoft\User Account Pictures\Default Pictures
Windows 7
These pictures are 128x128 24 bit. The path to the default account pictures:
C:\ProgramData\Microsoft\User Account Pictures
This is a hidden directory that will not be visible unless you goto Explorer and enable view of hidden directories.
