even if you do a clean install, your partitions should stay the same. you would only have to format the side with windows installed on it (if you do a clean install). if you have any Programs installed on your other partition, you might run into some problems launching them once you put on PRO. So to sum it up, Your DATA storage partition can be left untouched, and you can do a clean install on your WINDOWS boot partition side.
word of caution: if you can, back up your files just in case.