Sorry, didn't catch the beginning of this thread.
Did your version come pre-installed?
If it did, the OEM (Original Equipment Manufacturer, such as Dell),
sometimes loads the program from a different disk to the one they supply you
with.
When trying repair/reinstall, the system may be looking for a file that does
not exist on your supplied disk.
You need to download Windows Install Clean Up Utility
http://support.microsoft.com/default.aspx?scid=kb;en-us;290301
The download link is under More Information.
Use this to remove any registry (remembered files/settings) files relating
to original install and then do a fresh install from supplied disk.