You'll need the setspn utility. You can get it here:
I've run it from XPSP3 and Server 2003. You just need an account with sufficient rights to do admin work on the domain.
Once you've got that you can run it against the server's SPNs.
To list the SPNs currently assigned to the server:
setspn -L server1.domain.com
A typical delete command would be like this:
setspn -D MSSQLSvc/server1.domain.com:1433 server1.domain.com
If you need to remove the SPNs from an account (the opposite of what I needed) you have to run ADSI edit to get to that information.