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Is there a way to change Mount-Point after installation of elementaryOS?

I have recently installed elementary OS on a USB drive from a system running Windows 10, but I booted live from elementary OS DVD for installation purposes.

Now every time I boot my PC without the USB drive, an error is displayed:

error: no such device:

error: unknown file system

Entering rescue mode…..

grub rescue>_

From what I learned it seemed that I need to reinstall the OS and change the mount point to where the windows partition is located, but I have already done many changes to the OS so I don’t want to lose any of it… So is there any way to change the mount point without reinstalling or any other way to cure this disease?