Just FYI, I haven't compiled or tested these on 64-bit systems, but for SQL 2K5, I'd highly recommend using the SQLCLR and built-in functionality.  On SQL 2K5 XP's are deprecated, and the SQLCLR code is much easier to maintain.  Creating regular expression matching procedures and functions using .NET and the SQLCLR is relatively simple.  Just my .02.

Thanks,

Michael