yes, it took 17 hours on mine too, but we would have never found those problems anywhere else.
I too had the same issues.
http://pcsupport.about.com/od/toolsofthetrade/ht/sfc-scannow.htmhave a look at this section.
Tips: 1.
When running sfc /scannow from outside of Windows, like from the Command Prompt available when you boot from your Windows disc or flash drive, or from your System Repair Disc or Recovery Drive, you'll have to tell the sfc command exactly where Windows exists, as in this example: sfc /scannow /offbootdir=d:\ /offwindir=d:\windows
The /offbootdir= option specifies the drive letter, while the /offwindir= option specifies the Windows path, again including the drive letter.
lastly, do you have another computer with the same system or install disk?
shane can/should be able to tell you how to run the SFC scan from your install disk using this method:)
UNTIL you run SFC clean, only solution, install a new harddisk and all your programs.
then, before you copy any files. understand what not to copy to your new system...
maybe shane even has a USBboot disk for you to use?