Do I have to start over ???

[Luke2]

I'm about to build my 1st computer, and since it's my first time I have a question about all my data...I will be keeping my Hard Drive with 70 GiGs of Data on it...So when I put all the new stuff (As a Mobo,VC,PSU,CPU) will I be able to see the Data on the HD or do I have to re-install the whole system ???
THX UR REPLIES !