It can be tricky without looking at your settings and resulting partition map. It cab be a little late, too. (I don't say the problem is not solvable.)
Usually, it's better to install Linux after Windows; it's much more flexible and can arrange all the partitions properly. The idea is that Linux installs master boot which uses GNU Grub multiboot loaded in the regular Linux partition.
See Grub documentation (
http://www.gnu.org/software/grub/[
^]), maybe it's there but Grub don't show both because it was not configured for Windows.
Which one is loaded by default? If Linux, the situation is much easier, as you can always access all partition and Grub data. Normally, Linux access all partitions including NTFS, but Windows can only access NTFS and FATs. There are a number of good third-party Windows tools to mount and access Linux file systems.
—SA