chosing to install over windows.

I spent today setting up and backing up files on an old computer to learn linux on. I downloaded several copies and the first one I went with was ubuntu. While I was setting up the install I chose to install over the current installation of windows, assuming that it would choose the drive and partitions related to the current windows installation. However it did not, to my horror 30 minutes later I discovered it instead chose the backup drive I had connected to the computer to back up the files I wanted to save on the computer before I wiped it. This is a gross error on the part of the ubuntu programmers. I don't know why it chose that drive, but I will include a list of difference between the two drives. The back up drive was larger(1Tb) and connected via usb also is newer western digital, while the drive I had intended was smaller(250Gb) and connected through IDE also is older maxtor. The Mobo does have the ability for raid but no raid drive was connected.

I cannot express the grief this error has caused me, my entire last 10 years of meticulous backing up and saving of old content and computer projects both programming and musical have been wiped out, not to mention the years of digital pictures now lost(Very fortunate that due to convenience that the pictures taken since the my children were born were all loaded on to the macbook and not this drive.) I have not done anything to this drive since the install and any aid in undoing this damage would be appreciated.

-Norm