Cannot dual boot after installing Windows 8

Hi

I had a 500gb disk split into a couple of partitions a small system partition, then approx. 220gb for window vista (original when purchased) and a windows 7 (later added).

I recently purchased windows 8 and installed this to the vista partition, I formatted the partition during the install process.

I wanted to keep my windows 7 and 8 with the OS selection when booting, but now when I boot it goes straight to windows.

I have gone into the startup & recovery setting section under the advanced tab of the computer properties window, but while it says to display the list for 30 secs, when I try the dropdown box for a default OS there is only the windows 8 showing. Does this mean that my windows 7 is gone?

When I look at the partition that it was on (shown as a separate drive under win8), it would appear that everything is still there.

Is this a problem with MBR?

HELP! Need to be able to dual boot.
Thanks