partitioning - Should I backup my data partition before installing Ubuntu?

I have my HDD with two partitions (C:\ with W7 on it and D:\ with all my data). I really want to leave W7 behind and get my laptop only running Ubuntu :). When I run the installation CD, ¿will it delete my D:\ partition as well? Or can I install Ubuntu just fine without backing up my D:\ partition? I appreciate a lot your help.