老革命碰到新问题. XP activation woes

Just installed Dell laptop's OEM XP on my desktop yesterday. It asks me to activate this XP within 30 days.... I scrambled to find a valid 5x5 serial number from the Internet, and then it gives out a long string of digits and asks to call customer service for a 7x5 serial number. This is extremely painful. Any suggestion to beat this problem?

As a matter of fact two days ago, I also installed it on a second Dell laptop (very old one), it makes no noise whatsoever. Upgrade to SP2 was smooth too. So should I install this OEM XP on my DEll desktop and later ghost it over to other non-Dell PCs? Any help is appreciated

Heartbroken here.