Normally Windows XP would lock you out completely after a while if you don't activate. But there are a lot of exceptions, like volume license keys, certain OEM

Normally Windows XP would lock you out completely after a while if you don't activate. But there are a lot of exceptions, like volume license keys, certain OEM install discs, certain VM images released by MS, and ahem unofficial ISOs with things like AntiWPA slipstreamed into the install.