Hello everyone. I'm having trouble with an iMac I have in my house which I'm trying to repair so that I can sell it. Let me explain the context: I received this iMac about a few months ago from a friend. He had asked me to add more RAM and sell it. The iMac is the early 2006, 20 inch, Intel Core Duo version. I had Leopard installed and 1GB of RAM (2 x 512MB). My friend wanted me to add 1GB more of RAM so I purchased 2 x 1GB SODIMMs compatible with this iMac. I installed the RAM and at the same time, reinstalled Leopard. When I booted it up with new RAM and new OS installed, it would work for a few seconds and then it would freeze completely. It was like if the computer had stopped reading the hard drive. Immediately I thought it was the RAM since it was the only hardware change I had done. I talked to the seller and he told me that it was his own personal memory and that it worked fine so I burned a copy of memtest86 and ran it a few hours completing many cycles. I didn't get any errors so I ran it a complete day looking for at least one but nothing showed up. I then swapped the RAM for the old one which I was sure worked and nothing, the same problem, a freeze about 20 seconds - 5 minutes from booting. I then thought it was the internal 250GB hard drive. I took the Mac apart and removed the hard drive and replaced it for one I had which I was sure worked. Installed the OS and it wouldn't even install. When I had to select which drive to install the OS, sometimes the drive would disappear like if there where nothing inside. I ran HD Tune + on the original HDD and no errors popped up. I ran it in my drive and no problems once more. At this point, I was about to remove hardware from the list of possible problems but I ran Disk Warrior 4.4 and here I had more problems. When I inserted the Disk Warrior disc, it would sometimes boot from it and other times just spit it out. When it did boot, I would perform a function to repair the drive (I'm not sure what the function was, something like permissions or disk repair or something, whatever, not important). However, when I did this, it worked fine for a while and then it stopped recognising the drive (just like the OS X installer did) so there I got very confused and couldn't think what would cause this problem. Today, I have the Mac with Leopard installed but won't work and Disk Warrior won't boot and I don't have anymore resources for trying things on it. The installation of Snow Leopard (yes, I tried installing it a few times in the middle) would always die at the same point, telling me some files couldn't be read or copied or something like that (this is how I jumped to the conclusion that the HDD might be the problem). For the record, both Leopard and Snow Leopard where installed from an external Hard Drive but I don't think it's a problem, I've read I can do this with no problems. Anyways, I would be really happy if anyone would share a tip or piece of data that might help me get done with this machine. It's been 6 months since I have it in my hands and I just want to finish with it. Thanks everyone for taking the time to read this and if you have anything that might help me, I'd be very glad.