Here is what happened.
Windows is dumb. It thinks that it's bootloader is the best, thus when installing windows 7, it will install itself over grub. No since windows is dumb, it can't see the ext file systems, so it can't tell that grub is there. You see two answeres above. The first one suggests neosmart easybcd. That is a fine option, probably the easiest, but there is another. The boot repair disk.
Why the choices?
With easy bcd, the program adds Ubuntu into the windows boot loader. With boot repair disk, it reinstalls grub2.
So it's your choice. Do you like the (ugly) windows boot menu, or the very customizable (and awesome) grub2 boot loader.
Most people would rather go with grub.
I would install grub, and then burg. Google burg.
This isn't so much a Ubuntu related question. Of course, boot repair disk is based off of Ubuntu core files, though.
Every time you install a new version of windows, you will need to boot into the boot repair disk, and reinstall grub to the MBR.
You'd think windows would just give you the option to write wbm to the MBR :)