Additionally, find out what's in your windows temp directory and delete them all. Easiest way to find your temp is to:
Control Panel, System, Advanced, Environment Variables and check for the variables TEMP and TMP. Clear all the directories you find by deleting all the files (usually you don't need these files but verify anyways).
Second thing to check, make sure you are logged in as administrator.
Third is to try with auto scan disabled if any virus scanners are running.
Fourth is to copy the installation files to a dir in your hard disk and install it from there.
Last, verify you have enough disk space in your system.
HTH / Good Luck.
Stone walls do not a prison make,
Nor iron bars a cage;
Minds innocent and quiet take
That for an hermitage;
If I have freedom in my love,
And in my soul am free,
Angels alone that soar above
Enjoy such liberty. - Richard Lovelace