Hello, I have been a Mac users for four years but have finally signed up at the Macrumors forums because of my iMac. This is the white iMac, with a 500GB Seagate HDD (7200.9, ST3500641AS) nVidia 7600GM and has an Intel Core 2 Duo chip at 2.16GHz. (In case these specs might help in your response.) It broke down last october during an installation of Leopard. I sent it to a local Apple-certified service provider here in Singapore and was quoted that the HDD crashed and needs to be replaced. I did not go along with the repair because I wanted to save on cash and DIY. Just a few days ago, I finally got into it. I bought a Wester Digital 500GB (didn't wanna go any bigger in case any heat problems arises), it's one from their "Blue" series, WD50000AADS. I replaced it with no problems with directions from this website (http://home.comcast.net/~woojo/DFFA53A0-F23D-4541-9015-481FD3B6532E/iMac_Disassembly.html). I have the retail versions of both Leopard and Snow Leopard and I tried both. Starting up the iMac gives the folder with the question mark sign, and upon inserting any of the install DVDs and pressing "C" both the discs up. Upon reaching the stage of the installation asking me which HDD I wanna install Mac OS on, there was no option for me. Using Disk Utility, I could only see the install DVD and not the new HDD. I thought maybe I need to format it. I took it out again, put it into my 2-bay HDD enclosure and it can be detected on my MacBook Pro (Late 2008). One partition formatted in HFS Journaled. Doing this did not help and the install DVDs still could not detect the new HDD. Any ideas, guys? Thank you for reading my lengthy post. I wanted to make sure I was thorough with my explanation.