First of all hi! Just wondering if anyone can offer some help on a problem I'm having... I have had an Apple iMac for around a year now (20" Intel Core2Due 2.16mhz late 2006 model just before they went Aluminium) and recently found that I needed more hard drive space. After reading up on disassembly guides I decided to give it a shot myself to save some cash. I had a spare Seagate 400GB drive doing nothing in a cupboard and decided this should be enough of a jump from the 250GB that was already in the iMac. The install went fine but after rebooting and installing OS X I now have the HDD Fan sat on full speed (5000rpm according to iStat Pro) which is extremely noisy. After looking around it would appear that some people have had this issue and it can relate to a couple of different problems. The first of which was the temp sensor not being replaced properly, I checked this and it all appears to be fine and is still giving readouts in iStat so shouldn't be the problem. Some people have been able to remedy this with an SMC reset but this hasn't seemed to do anything since I have tried it other than the optical drive fan speed has jumped from a steady 800rpm to over 1000rpm. I have read that there was an issue with some early 2009 aluminium iMac's not liking new HDD's because of firmware not matching that of the original Apple HDD firmware but this is an earlier model so it shouldn't be the issue. Anyone out there have any idea on this and how to fix it? The iMac is out of warranty so taking it in to an Apple store could well cost some serious cash Thanks in advance for your help.