No you will not lose your songs. But you may lose your library if you don't do it right. How is your music situated right now? Is it all on one drive? Where is the library located?
Most likely in one of these locations
\Documents and Settings\username\My Documents\My Music\iTunes\iTunes Library.itl
\Documents and Settings\username\My Documents\My Music\iTunes\iTunes Library.xml
\Users\username\My Music\iTunes\iTunes Library.itl
\Users\username\My Music\iTunes\iTunes Library.xml
You can do a search on "library.itl" (without the quotes) to find where your library is. Here are a few tutorials on how to do what you want to do:
I am not sure what version of Windows you're using but here is more info: