There is a file named grub.cfg at /boot/grub directory.
You can edit that file with a text editor and change
a field several lines down like this

set default="0"

If you change it to

set default="Num"

The Num is a number is what you get by counting from the
top of the black screen down to your windows OS, counting
from zero of course.

Another tip is that when the black screen is up you can press
a down arrow and the count down will stop and you can read
the stuff on the screen and choose what you want to boot.
Comes in handy when you have several bootable partitions
of various OS's, in your case you have Windows and Ubuntu.
I have a windows and Xubuntu partitions and another I had
Mint 13 in and am trying to load Kubuntu in but it fails.

I hope this helps if you need to ask more questions feel
free to ask direct if you want.