pop up warning in PC Sync when downloading data from phone?

Hi I was hoping someone could answer this question
I just bought a data cable for my Virgin Mobile Snapper 8915
and used PC sync to connect
btw the port password is just your last 4 digits
took me awhile to figure that out
anyway when you click the (Phone to PC) tab a popup
warning comes up saying"If you receive cell phone data all
data in PC will be deleted" now I'm afraid to use it
it can't mean that it will wipe my hardrive??? can someone who uses PC Sync please confirm what that warning actually means? thank you