You'll need
StuffPlug-NG. But keep in mind that it is still in Beta and still contains some bugs.
Download it here:
http://www.stuffplug.com/SPNGMSN7.zip (this is the version for MSN Messenger 7). Then unzip it and install it. To complete the setup you'll need to validate the installation code, this can be done by visiting
http://www.stuffplug.com/?act=generate.
If your contacts use MSN Messenger 7 Beta too then they will need this plugin also, otherwise they will not see your oversized display picture. If they use MSN Messenger 6.x then they don't necessarily need it.
To make an oversized display picture with this plugin you'll need to enable that option in StuffPlug-NG in its configuration panel, and you'll need to add a new display picture and answer "yes" to "keep the original size".
Remember to not add an oversized display picture which is too large!! Otherwise your contacts will be very annoyed. Keep the size down (do not add a picture which is 600x400 pixels for example). A good absolute maximum size would be 200x200 pixels. Big isn't always cool/beautiful...
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