Adding extra HD to Server mini tower

Hello fellowing users i have a newbie tech question.I want to ad a second hd to my system.It a Toshiba Magnia 510D.I am taking the hard drive out of an other same model. The drive has been already partioned and neither computer has an OS installed on it.I want to know would it make a difference If i just installed it or should i configure both as one drive.Thank you all for taking the time to read and respond.Any help welcomed. Mf255@excite.com