super noobish question,to put a hard drive into a new pc must it be formatted?

i want to put a hard drive from my old pc to one i built recently,do i have to back up all data and format it?or can i just plug and play it?:P

ok thnx

yeah ive pulled old hard drives and put them into new systems with all the operating systems and files intact. Try it and see it should work for you as well.