How To Retrieve Old Profile

My husband and I just bought a Dell Inspiron with Windows 7 Home on it. He bought it for use at work, and when he took it to work, they upgraded it to Windows 7 Professional. I don't know who they had working on this, but it seems that they didn't make a back-up of anything first, and my husband doesn't know enough about computers to have thought to make one, and he didn't realize that the people doing this to his computer might just not know what they were doing. Anyway, EVERYTHING he had on the computer before is GONE...right down to the drivers for the wireless and the BLU-ray disc drive. I can put that stuff back, but he had also just finished writing a sermon on the computer, and that's gone too, of course. A lot of work that unfortunately he didn't save anywhere else.