I ordered this old iMac on the first day intel macs became available. Jan 1 2006. It's been a great machine, but now it's time to replace the hard disk. I need a Serial-ATA (SATA) hard drive. One terrabyte or larger. It should be a 7200 R.P.M. drive with at least 8 MB of Cache memory built-in. And, it should be labeled as SATA-150 or SATA-300. Either will work, but I will only get the performance of the SATA-150 drive either way (the 300 will slow to 150 to communicate with my system). SATA-150 might be cheaper. The problem is that there are so many choices available, i just can't decide. It seems like there are thousands of disks i might use. Can somebody please make a recommendation, or at least tell me what to avoid? I am concerned most about heat inside the mac degrading the new drive's life expectancy. Cost is a factor, but i will choose reliability over price.