I don't know how to answer this question. I came in on a K-1 and then Adjusted my status to get the green card. Was I a lawfull non-immigrant? I don't really understand the wording. I don't remember signing up for any selective service, unless it was done automatically or something. I was 23 when I entered the USA and will be 27 when I mail in this form.

Are you a male who has lived in the United States at any time between your 18th and 26th birthday's in any status except as a lawful non-immigrant?

You need to contact Selective Services and explain to them. You were required to sign up for Selective services regarless of status between those ages if you resided in the US. You need for them to get you a waiver, otherwise you probably will be denied your N-400 during the interview stage...

Thanks, fortuantely I am not 26 for 3 weeks. Luckily I checked in time. So I have just mailed off the SS form.

Also I am not sure if there is a conflict of interest, but I am an ex member of the Royal Air Force, and still have a reserve commitment to the British Military for another 5 years.