Force manual system discovery in SMS 2003
Took me awhile to find this:
In the SMS 2003 Administrator Console, expand Site Hierarchy, then your Site Name, then Site Settings, then highlight Discovery Methods.
On the right-hand side, double click Active Directory System Discovery, then click the tab “Polling Schedule.”
Click the checkbox “Run Discovery as soon as possible.” The checkbox will clear once the discovery request is made.
Easy, no?