I'm pretty sure that you are going to comment back and apologize that you meant the opposite... but I'm going to quote you here...
There are things that I haven't tried yet... running Seatools in DOS such better for fault finding. changed the data cable and the PWR SATA cables.
So you are saying that you haven't tried changing the drive cabling yet? Your use of the past tense there, the period after the word "finding", and leaving out either "I have" or "I have not" before the word "changed" makes it a bit ambiguous. I'm not being a grammar cop here. More often than you would believe, people will do exactly what you did there, but then come back to explain that they were saying that they DID change the cables... which contradicts putting it in a paragraph all it's own that starts with "things I haven't tried". I'm just asking for clarification. Don't shoot me.
At any rate, if you know you should change the cables but haven't done so yet... that should be on the other list... the list of things you have already tried before posting for help. Same goes for any tools you already know about and feel are good at finding issues. You should have already tried these. In short, posting here shouldn't be a hand-holding experience. If anything, it should be AFTER you have exhausted everything you know of, so that you aren't responding to the people who answer you with "I tried that" and "I intended to do that" and "I thought of and dismissed that".
Have you tried a Full format instead of a Quick Format? Considering that a Quick Format doesn't access the whole drive. What's the results from that?
I've known drives that would start throwing errors after they were allowed to run for a while, but would read and write fine when they were cold. I've known drives that couldn't be read UNTIL they had gotten hot (that was one annoying week).
As has been suggested in the comments, you can use a program like Speedfan (download)to read the SMART data off the drive. As you suggested, you can use "seatools".... and from that (not from the information you actually supplied, which is ANOTHER thing you need to do) I can infer that you have a Seagate drive? You can download a copy of the Ultimate Boot Disc which comes with a number of HDD utilities. You can try the drive on another SATA port or in another computer... or in a USB/SATA enclosure. Definitely try another cable.
Diagnostics can be about inspired and logical guess work... but really, it's about having that list of all possibilities, and arranging them from the most probable to the least... and they trying them ALL, regardless of whether it makes sense or not. You'd be surprised how often the solution turns out to be one you would have dismissed.
1Where do you get the I/O errors? Did you already check the SMART values of the HDD? – speakr – 2012-06-15T12:58:09.380