From my research of this error it seems that the parition has been marked hidden during the install and that is why you get this error.
You will need to get Partition Magic or ERD Commander and boot from that. From there make the partition unhidden.
You could also do this from GParted. That should resolve this issue and allow you to use Windows again.
My results did not come from Google but from Microsoft:
Somtimes it is best to search right from the source than to use Google. Google is great but Microsoft does have agreat documentation of things as well.