just want to ask, you got XP with this machine when you got the PC from the shop? its not a burnt copy?? i have had people use programs like reset5 to wipe the Registration of windows XP, now that wipe the Registration but when they download SP2 it goes crazy and wont let them log back into there machine.. But what you have is a bad install of SP2, it happened to myself, well i made it bad becuase i turned it off while it was half way into install SP2. IF you cannot get into safe mode, try doing a repair install and hope you have not lost all your data.