So, had this hard disk (samsung HD501LJ SCSI) for a while now. A little while back when I first turned the system on, it would all seem to come to life, but would not output anything to my screen. Thought this might be graphics card, (evga 8800gtx), but now I'm not so sure. If I give the SATA cable a good shove into it's sockets on the motherboard and disk, the problem seems to go away for a short while. However, today was slightly different, as the screen showed stuff up until I expect windows to start loading, instead it said 'a disk drive read error has occured, press ctrl alt del to restart system' or something like that. So I just gave the cable a good wiggle, and then everything seemed to work fine. Is this problem just a loose connection, and if so what should I do? 

fixed, problem stopped for a while, then came back so after some fiddling just put SATA cable into different mobo slot... seemed like 1st port was loose.