Can you still boot to Windows 7? If you cant this might fix the problem with windows7 booting, and maybe ubuntu, but I have no experience with ubuntu except I know it can be a pain :
You could try booting to the Windows 7 dvd and when you get to custom install, click on repair, and see if it fixes the boot screen. If it finds something wrong it will ask if you want it to repair, select yes, and then it will prompt you to reboot -now there should be at least Windows 7.
When you install ubuntu you may have to create a new partition - delete the ubuntu partition, firstly, then recreate it in the empty space.