Convert a binary SID to decimal format in C#

Hi All,
 I've been tearing my hair out with this problem. Can't seem to find a solution. I hope you can help.
I have a web app in visual studio 2005 and use the System.Security.Principal.IPrincipal class to get the SID. This comes back in the following format (e.g. S-1-5-21-xxxxxxxx-etc). What I need to do is to convert this format into decimal (e.g 01050000000000051500...etc) from a web app in visual studio .net 2003

 
Anyone know a script that can do this?


Thanks,
Bobby
 
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