Comments
ProductType = 1(workstation), = 2 (domain controller), = 3 (member server).
One WMI filter can have one or more "select" clauses (see last example). 


WMI Filter Windows XP
select * from Win32_OperatingSystem where Version like "5.1%" and ProductType = "1"

WMI Filter Windows 7
select * from Win32_OperatingSystem where Version like "6.1%" and ProductType = "1"

WMI Filter Windows XP + Windows 7
select * from Win32_OperatingSystem where (Version like "5.1%" or Version like "6.1%" ) and ProductType = "1"

WMI Filter Windows 2003 (member server)
select * from Win32_OperatingSystem where Version like "5.2%" and ProductType = "3"

WMI Filter Windows 2008 (domain controller + member server)
select * from Win32_OperatingSystem where Version like "6.1%" and (ProductType = "2" or ProductType = "3")

WMI Filter Computer Name + Windows XP/7
Select * From Win32_ComputerSystem where Name LIKE "%pksa%" 
select * from Win32_OperatingSystem where (Version like "5.1%" or Version like "6.1%" ) and ProductType = "1"