Which exact model of Medion? (see the label)
Is there a Recovery Partition on the main drive? (Run Disk Management and have a look for a likely partition)
If you do have a Recovery Partition, it is possible to set it to boot from that.
But first, try your Boot options (eg F10?) to see if you get options that way.
You could also try booting from the CD you do have to see what options come up. It may allow restore from HDD Recovery Partition