folder with question mark on it

I Have tried that. The problem is the CD players doesn't work at all. Trued holding down the command + R and the folder comes back. Can't get to it by hooking up to another computer for the folder cones back. I have no idea how to get it to boot so I can install the operating system back on it. Nothing works. There is no recovery disk with this computer. It was bought second hand. It was working then it just stopped while trying to transfer to another computer. I need help with this one

Ok. I got pass that problem by reconnecting the firewire cable and let it boot up. That seemed to have fixed that problem but I did it the wrong way. Copied the wrong system and now I can't find some documents I had on the desktop. I am not sure but I thought that it only copied the system files and left folders. If so then could someone help me find out where to look on the computer for these documents there were on the desktop? I have searched on the hard drive but I don't see them. I see a couple of files I don't recall putting on but the ones I am looking for I don't see. Thanks in advance.

It is a Mac mini (mid 2010) running Yosemite 10.10.2 with 4 GB ram, 2.66 GHz Intel Core 2 Duo. This was suppose to be something straight forward and it turn into a knightmare. Thanks again for your response.

I Was migrating from my Mac mini to a mac tower 8 core running Yosemite 10.10.2 with 16 GB of ram. I got past the problem with the folder. What I did wrong was I thought I was migrating from the. Mac mini to the tower but that is not what happened. It went the other direction. Now I have de stop documents I cant find on my mac mini. Not sure if they were erased or not. I didn't think that it would erase documents on the desktop but put them into a folder. Isn't it just suppose to copy system files? I have some important files on the desktop and would like to recover them hopefully. Both computers are up and running. I am coping files from the mini to the tower now because I am afraid to try that again. All my apps are still on my Mac mini but I will have to relegated most of them. I don't have a problem with that. I just need back the contents of my old desktop folder to copy to my tower if all possible. Any help in this matter is greatly appreciated. Thanks again.

Thank you for your reply. The case is now solved. Appreciate the help very much. Thanks once again.