You did a clean install of 7, correct ? Whether clean install or upgrade, unplug all the external devices including network cable, modems, printers.
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8 hours is hard to believe, are you sure it does take that long ? Did it also take much time to install your previous versions of windows ?
In theory, it can take that long if your installation disk is corrupted or if your DVD drive is malfunctioning. If you have hard drives connected in a RAID, it may be the cause due to smth with your RAID controller.
In Windows 7, try to copy large blocks of data (e.g. 500 Mb) from one place of hard drive to another, to see if your hard drive is working fast enough.