Debian boot problem
I installed Debian(I think it was called Etch) on a Dell P3 laptop and the display was not right. It looked as if it was trying to display two identical images on top of each other. I took it to my local genius kids store and the guy said,"do you need 3-d?" Not thinking I did since I was interested in the music angle I said no. He then typed at the speed of light for about 10 seconds and said, "there! fixed!" I asked what he did and I think he said something about a display driver. I'm not sure. He spun on his heel and disappeared into the back room before I could waste any more of his time.
My question is; what did he do? and how do I fix this myself in the future;