I work for a non-profit, so we rely on donated computers. My PC died, so I upgraded to a Power PC iMac. I transferred all the files with a 3GB flash drive, took me about a week. The iMac lasted a year, until one morning there was an explosion from behind the white plastic enclosure and smoke poured out of the long slot in the back of the iMac. Luckily for me, I had just received another donated iMac (Intel-based) a couple of days earlier. Of course, I didn't have a backup of my data on the old mac, so somehow I needed to get the data off the old powerPC imac and onto the newer intel imac.
Used iFixit to remove the hard drive from the PowerPC iMac. Nice series of pictures made it a breeze. Had to order the tools from amazon, but that was a breeze as well due to iFixit's excellent tools list. When I opened up the iMac, I learned that the fan and/or heat sensor had gone bad and fried the motherboard. Removed the hard drive as per instructed and ordered the recommended drive enclosure from iFixit. The instructions in the enclosure were quite easy, and got the drive installed in no time. Connected the old hard drive in the enclosure via USB to the new iMac and the old hard drive would not mount. Tried to use Apple Disk First Aid to repair but it would not even diagnose the problem. Used the iFixit forum (Answers?) to look up what to do, and downloaded a drive utility called DiskWarrior. DiskWarrior diagnosed the problem and fixed it in less than 5 minutes. Rebooted both the drive enclosure and the iMac, and the hard drive mounted this time. Transferred all my old files onto my new imac hard drive in a little under an hour. Now I used the old hard drive in the enclosure via USB as my Time Machine backup, and run all my files off my iMac Hard Drive.
Paid a wee bit more for the parts on iFixIt, but the shipping was reasonable and quick (From CA to HI in 2 days) and I felt really confident that I was ordering the right thing AND that it would work. Plus, the $5 discount helped as well. Also learned the Apple Disk First Aid utility is pretty weak. Lastly, want to thank iFixit for the awesome directions and pictures. People in my office think I am some kind of Mac wizard now.