Will my secondary HDD be erased when a clean OS installation is performed?

My mom happens to have a secondary 160GB HDD that she has absolutely no need for, so I thought I'd ask her if i could use it as my secondary (just for computer tech experience). I am however going to install W7 (clean, since i'm going from 32-bit to 64). Would that HDD be wiped if I left it in at that time? If so, can I simply disconnect it and then reconnect it afterwards? It would be a very convenient way for me to backup my files (pics, movies, save games, docs).