Ubuntu will happily dual boot, provided you give it a partition and tell it to do so. I suspect you may not have done that. Very possibly, you told it to use the whole of the drive, so it did.
click here for a page I wrote concerning installing PCLinuxOS. Although it's noy Ubuntu, the installation process is pretty much the same. Take particular note of the partitioning process. Did you do something similar?
Can you access Ubuntu OK?
If you can, what does the file manager show in terms of your hard drive(s) and partitions?
Whether you can recover anything depends upon the result you get from above.
You can also open up a terminal and type the following command:
sudo fdisk -l
It will ask you for your password, type it in and hit Enter again.
This will give you the Hard drive output data. Use copy and paste to post it back here.