PC World, purchased it 1 week ago today. No problem with it so far except for the yellow tinge which is not that bad, I'm on week 49. PC World give 28 days to take it back with a fault, I consider the yellow tinge a fault, is this enough to be able to take it back? In some ways I am unsure if this is what I should do as I got a 10% discount off the screen price from PC World as in I told em I wouldn't buy it unless I got the discount, they were a little agitated but gave the deal. I'm not so sure I'd get the same deal again. I am of a mind to actually take it back and wait until they start shipping new iMac 27's without the yellow tinge though. I note that the UK has no stock of new screens for them and I really don't fancy having to wait until they sort the supply problem out. Being new to Mac (loving it btw) what/how do I successfully clear all my data off and return the item back to standard from switched on. Also, when first loading it it asked me to register with Apple which I duly did, how do I de-register if I take it back and do I have only 14 days to do this with Apple as opposed to the 28 day return/exchange policy that PC World tend to operate. Only problem I have found with the machine other than the annoying yellow tinge is that on two separate occasions it has not allowed me to shut down, I've used the force quit function to shut down anything that looks like it's open but when I hit the shut down tab it just won't shut down leaving me to do a hard shut down as in switch it off at the mains and disconnect it from the socket which of course cured the problem. I have loaded all available updates to the machine one of which fixed the flicker.