Dual boot configurations should have separate partitions or separate hard drives for the individual OS. You've got a messed up installation there, with both OS somehow installed on C, i.e. on the same partition. If you had a proper dual-boot configuration, I think you would find Win XP Pro is not noticeably slower than Win XP Home.
Honestly, the best thing to do in this case would be to format your hard drive and do a fresh installation of Windows (whichever version you prefer), and maybe setup a proper dual-boot configuration. But, if it were me, I'd just install Win XP Pro. Why have a dual-boot configuration with the two versions of Win XP?