Yes, it is inside registry.
HKCU>Microsoft>MSN Messenger>PerPassportSettings>
Your Special ID Number If there are several keys there and you cannot find which one is for your settings, then download and run this small tool to determine your special id number
MSN_ID.zip (If you cannot open this file, it means there is hotlink protection on it, so try every ID you'll see there. If you want I can even attach that program here) When you find yours, click on it and at the section at right hand side, find DontShowDefaultSignIn and set it to 0.
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