Use WinRAR To Split Files

WinRAR does more than just compress data. It can be used to split up big files so they fit on multiple CDs for mailing purposes. Choose a file or folder you want to split and choose to compress it by right-clicking on it, and clicking "Add files to archive". Click on the drop-down menu for "Split to Volumes,bytes". Enter a value in KB or MB or choose from one of the presets and click OK.