It looks as though the answer to my question is here;
Update ASP.Net membership from windows service
However I cannot get any recognition for the namespace; System.Web.Security. I try to add a reference to System.Web and I get;
Could not resolve assembly “System.Web”. The assembly is not in the currently targeted framework “.NETFramework,Version=v4.0,Profile=Client”. Please remove references to assemblies not in the targeted framework or consider retargeting your project.
Preet is right, I found the solution here;
http://social.msdn.microsoft.com/Forums/en-US/netfxappcompatprerelease/thread/ad71e8e5-3124-47de-89cb-97b1d2d4263a