Is there a way to merge user profiles on xbox360?

It seems that the only way you can do it is if you have one profile that is offline and one that has a registered gamer card on Xbox.com (this second account can't be on Xbox live). I found this link on Xbox.com which gives you step by step instructions on how to combine the two profiles:

http://mktplassets.xbox.com/NR/exeres/7239CD88-DE65-408D-AE16-0FC0F8CB4230.htm

If your other profile is on Live then unfortunately, at this time, there is no way of merging the two profiles.

Hope this helps.