Do you have any partition in the hard disk? How much space do you have in the primary hard disk? I ran into this problem last year when I was using IS Express. It by default copies the setup file as it is in its original size to downloaded folder of the computer. So If the computer has only 2 GB space in C drive (very unlikly, but in our test box though), the original file as 480MB and unzipped was alomst 1.4GB and windows keep complaining it can not complete because there is no space.
My 2 cents.