Are you booting a live usb, or a dvd to do this install. Or are you installing from Mint
onto you computer while running windows 8? Like are you using
A windows OS installer?
I used A Mint 13 amd 64 maya mata from http://distrowatch.com
I down loaded it and put it on a usb thumb drive, or you can burn it
on to a dvd.
Then I changed my bios to boot off the usb, or dvd.
Shut computer down and reboot.
i have done 20+ install, mostly linux operating system in my life. some are good
and other buggy crashers.
I have not used window to install another linux for past 10 years,
and that was when "partition magic" and "system commander" were king
installer at the time.