Setting A Password Policy for a web site in c# 2008

Try this.
^([A-Z])([a-z])([+!_%&])([0-9]{5})

([A-Z])- will allow only if first letter is caps
([a-z])-secondletter shud be lowercase
([+!_%&])-third character shud be symbol.I have added only few.
([0-9]{5})-then it should be followed by 5 digits

Regarding password should expire in 6 months, you have to set that in Database. in User table have password changed date, where you insert current date and whenever user logisns, validate it crossed 6 months or not

sample code:

ErrorMessage="RegularExpressionValidator" ValidationExpression="^([A-Z])([a-z])([+!_%&])([0-9]{5})" ControlToValidate="TextBox1"/>