To dual boot you will need a partition or drive to install to. Do not try to install XP to the same partition as Win2000 if you want both.
Totally agree about XP Home and Pro.
The only real reason for choosing XP Pro over XP Home is if you wish to be part of a domain network or a simple network which has more than 5 PCs. In just about every other respect the two are identical in every way except default settings.
Copy all the data you wish to keep, including your Favorites, Outlook (if you use it), etc. onto a CD (if you have a burner), a USB flash drive (again, if you have one), or, if nothing else, a floppy disk.
Note: If you don't have a CD burner or USB flash drive, you really should consider it as they aren't very expensive nowadays -- and very handy!