I think this falls under the 'unsupported' umbrella by Microsoft but it is nice to know that it is at least doable for installations that don't need/want MSDE and would rather use the 'real' SQL for their WSS sites. I do believe you might be able to trick WSS into using SQL 2005 Express with WSS 2.0 SP2 but I could be wrong on it. I haven't tried it out personally but would be curious if anyone has had any luck with it.
Link on the details:
http://weblogs.asp.net/jan/archive/2004/02/03/66544.aspx
