Manually Force XP Workstations to WSUS

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate]
"WUServer"="http://Replace with WSUS Server IP"
"WUStatusServer"="http:// Replace with WSUS Server IP"
"TargetGroupEnabled"=dword:00000001
"TargetGroup"=""
"ElevateNonAdmins"=dword:00000000

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU]
"NoAutoUpdate"=dword:00000000
"AUOptions"=dword:00000004
"ScheduledInstallDay"=dword:00000000
"ScheduledInstallTime"=dword:0000000a
"NoAutoRebootWithLoggedOnUsers"=dword:00000001
"AutoInstallMinorUpdates"=dword:00000001
"RebootRelaunchTimeoutEnabled"=dword:00000001
"RebootRelaunchTimeout"=dword:0000003c
"RescheduleWaitTimeEnabled"=dword:00000001
"RescheduleWaitTime"=dword:0000000f
"DetectionFrequencyEnabled"=dword:00000001
"RebootWarningTimeoutEnabled"=dword:00000001
"RebootWarningTimeout"=dword:0000001e
"UseWUServer"=dword:00000001
"NoAUShutdownOption"=dword:00000000
"NoAUAsDefaultShutdownOption"=dword:00000000

Open up a notepad
Copy the text.
Change Replace with WSUS Server IP
Save it with .reg extension
Run it
Reboot