Shoutbox

The actual folder changes depending on the logged in Windows user, and your Messenger address. The full path is therefore:

C:\Documents and Settings\<WindowsUserName>\Application Data\Microsoft\MSN Messenger\<MSNHash>\UserTile
UserTile = Display Picture

<MSNHash> is an unsigned long (between 0 and about 4 billion) that is calculated from your e-mail address.

Note: All your Display Pictures are saved as files with names like TR*.dat. They are in fact PNGs, so just chenge the extension.