First, find the friend and confiscate his "free advice and worth every penny" license........
Now you know that installing something (anything) to a hard drive will overwrite anything that is there. But that is not precisely correct, so there is hope......
In you case, you apparently let Ubuntu have the whole disk. First it set up a filesystem stucture, and then copied its files. Presumably, this did not fill the disk. In the space that is left, what you have is:
1. the new filesystem structure.
2. the remains of whatever files were there.
The most commonly recommended tools are "testdisk" and "photorec". (Both are by the same author---just Google "testdisk" and you'll find them. Since you have used the whole drive, you need to run these tools from another drive or from CD (Don't know if these particular tools come this way.)
One way to go is to simply install your drive in another computer.
If the data is valuable, you should clone the drive before playing with it---If it is REALLY valuable, you might be better off with a professional recovery service.