what you wrote is not very clear sir.
you said you installed xp pro on a seperate partition? then xp home should be on the other partition and easiliy accessible. you'll just need to configure your bootloader.
however if you had to reformat your disk to make the new partition, then you lost your original installation of xp. if this is the case, you will have to reinstall xp home.
btw, rumour has it that xp pro is better than xp home.