thank you for all the feedback andavari and sandra ccleaner!
i ended up "cleaning the free space" and then running dban. i'm hoping this will be sufficient!
i want to sell my old windows xp computer but need to wipe the drive first. will it be safe enough to clean the "empty" areas with ccleaner? if so, how do i get an older version of ccleaner that would be compatible with windows xp?
thanks!