The easiest way is if you have a CD burner or zip drive on the old machine or portable ones. 2 other options are to "borrow" the CD burner from the new machine and put it (and some software) on the old one to move the files. Another option is to take the hard drive out of the old computer and put it into the new dell and copy the files directly. Then you can format the old disk once you're certain you have everything you need. A full format will erase all of the data on the computer short of having a data revoery place or the FBI taking a swing at it
