Originally Posted by
ProgrammingAce
Sorta, it'll cost you $12 though, and you'll loose whatever time is left on your Xbox Live Gold Membership.
You have 2 profiles, the one that's connected to xbox live we'll call Name1 and the offline account with your saves called Name2. Go into the dashboard and pay 800 points to rename Name1 to anything else (doesn't matter what). Now upgrade Name2 from an offline account to an XbLive enabled account.
Now, your XbLive account will have your halo saves, but you'll loose any saves for any games you've played since signing up for XbLive.