I have replaced windows 8 with ubuntu 12.10 , and after installing i can't open hdd and i get this Message
unable to mount location
I have very important files on my hhd therefore I can't formate it. What should I do to get to my harddrive?
From your comments I think that you have formatted your drive before/during installing Ubuntu. The fact that reinstalling windows also asks for a format confirms this: windows cannot use the Ubuntu file-system.
This means that you should STOP adding stuff to your harddisk. No installs, nothing. If you want any chance of data-recovery, you need to start doing everything from a live-CD or a USB.
Data-recovery is hard. You formatted everything. It is next to impossible to help you with this online if you have limited knowledge yourself, but I can explain the path you can hope for.
try to run a live disk to access your data and get backup of it