I am having a lot of trouble with my mac.

Question

About a week ago I wrote a question about the flashing question mark when starting the computer. After many days of having that problem, I manage to make it work by unplugging the battery and when starting holding the option and shiftt keys. However las Sunday I manage to make a bak up of the information in my mac and reseted the computer. When I reseted the computer it was working all ok.
I have to make clear that at this time, the back cover had no screws in, as apparently without the screws it was causing less problems.
Once the computer was reseted and the software were working fine, I decided to put the screws back in. ( I had turned the computer off to put the screws back).
When I turned the computer on again,  the question mark Icon on the file came up again. Reason which I turned it off again, unplugged the battery press the power button whilst the battery was unplugged to some sort of resetting.  Plaggged the battery in and worked. It was only telling me that the date and time were back in 1/1/2008 and changed it to the actual date and time. After that the computer was fine starting up with no problem. I decided to ask my huisband to put the screws back in for me. ( I wasnt sure if it was me putting them back in very tight) when my husband put the screws back in, the computer started to play up again. When I came home from work I started to try and make it work again, as I had done before unplugging the battery and pressing the power button whilst unplugged etc. and didnt work. I called then to apple support, and he told me that it was a very weird case as the screws has nothing to do with the operative system or software.  He told me that holding: comand +option+control+shift would do the same effect as unplugging the battery. However he also told me that it could be a problem with the hard drive as the file with the question mark was very frequent and that it happens when it cannot find the system to run. After talking with him, I tried the 4 keys as he told me but I think that in one occasion I release one of them and the computer turned on and I kept holding the 4 keys. After that, didnt start, so my husband told me to reset the compute again, and put in the "snow leopard" cd to reset the computer.
in addition to that and to top it off, when I was running the installation cd, it only goes to "select the disk where you want to install" but it doesn't show any disk to select and when I try to eject the cd doesn't work either.
Could the fact that I pressed and hold the 4 keys, command, option, control and shift at the time and I accidentally turn the computer on holthing them together have cancelled the disk or deactivate it?
I don't know If I have made my self clear or not. But need oppinions or if someone knows what can b wrong and what can I do?
Thank you all for the help.

Answer 1

It sounds like either your hard drive or the SATA cable that connects it to the motherboard are failing. This could be heat related in your case, which is why you see it after it runs awhile. You can take it to the Genius Bar for a free evaluation. If you decide to test it yourself, I usually suggest moving the hard drive to an external enclosure. If it works there for awhile, the cable is probably the issue.
http://www.amazon.com/Sabrent-2-5-Inch-Aluminum-Enclosure-EC-TB4P/dp/B005EIGUD4/ ref=sr_1_3?ie=UTF8&qid=1397647657&sr=8-3&keywords=2.5+enclosure
http://www.ifixit.com/Device/MacBook_Pro_13%22_Unibody_Mid_2009