If I already have data from my previous windows partition, what option should I select in the boot camp assistant?

I still have data from the previous windows 7 partition, but the partition itself doesn't seem to exist. I'm able to see BOOTCAMP in disc utility, but when I click on the "Remove Windows 7" option, the partition doesn't actually show up and neither in the startup disk list in System Preference. I'm using OSX 10.7.5. If I have to remove the windows 7 part to reinstall, will my data be saved, or do I have to back it up? And if so, does anyone know how to do that?