you will need to do this
if the Operating system on the old boot drive is from a manufacturerd PC soemtimes this wont work, because the OS is lookign for manufactures code on the motherboard or bios ????? i guess just give it a whirl
you know its easy to add your old drive as a slave, then you can get your data copied to the new system. You dont have to boot from the old drive to do that!
or does the new system not have an OS and your hoping to salvage the OLD OS and get it to work on the newer machine ?????
often times this approach does not work, when win xp senses a major change in the hardware inventory (HAL= hardware abstract layer) it will trigger the need for re-activation; a call to Microsoft, which under some retail
OS versions that may or may not grant you re-activation. If the old system was an OEM version they definetly will not grant you re-activation numbers.
if this is the case then buying a new copy of win xp will be your best route ? now that windows vista is on the market XP is very cheap on ebay @ around $80.00