New build and partition

[iKon]

I have just finished building my 1st pc for years and have got it running pretty sweet with my programs installed. My question is can i create a partition of the whole used area of the hdd, thgen if something goes wrong or i want a freash install just boot into this partition?

Thanks for any help

 

[iKon]

So i have an old hdd from my old pc, do i clone the new hdd? If i plug the old hdd onto new pc wont it conflict as it has XP on it? How will the pc know which to boot?