Saying you have a fresh clean laptop probably makes the odds it is this problem small, but I had similar symptoms from not enough space on the C: drive (it needs more than 6 GB available -- more if you'll also be installing on that drive), even though I wasn't installing on the C: drive. Here is the forum thread that describes what I observed and workaround possibilities:
http://forum.cakewalk.com/tm.aspx?m=2668496 The other possibility may be if one of the earlier part<x> files is corrupt -- apparently a number of people had issues with that (sorry I don't have thread references handy). Some consensus on that seemed to be not to use Internet Explorer to do the downloads (or to use a download manager if you did), but I used Internet Explorer 9 for it with no corruption problems (I did have a few aborted downloads en route to getting there, but I think that was issues with my slow DSL connection and then the expiration of the files from the earlier load attempts).
In either case, if you note which part file you are on when the error occurs, it should be that the one that isn't getting unpacked correctly is the one just before it, so, if it is a corrupt file, rather than running out of space on your C: drive, you'll know which one to download.
Rick