I have installed WSUS server recently and i don't know why some Windows XP clients are not getting detected. I have tried rejoining the domain and using "wuauclt.exe/detectnow" command but no avail. They simply show red indication in WSUS server. I am not able to make out if there is something wrong with WSUS server or those Windows XP clients. I want to know if there is some other thing that i can try out for forcing the client machines to get detected by WSUS server.