I'm posting this to help others who may need to try the same thing, and run into some of the issues I did. Primarily my purpose is to share solutions but also observations and recommendations. To begin - My MacMini was shipped as a 1,1 with 60GB HD, intel 1.5ghz Core Solo CPU, 1GB RAM, OSX 10.4 Tiger. Thanks to help from this forum, I debugged and upgraded it to 2GB RAM, a 2.33GHz T7600 Core2 Duo CPU, and flashed it to a 2,1 personality. So that's how it is today, and how it was when I upgraded the HD to a 500GB Western Digital 5400rpm "blue" drive. The "migration" was accomplished by using the OS's Disk Utility to "Restore" the internal HD to the new drive, plugged into a USB 2.0 HD Docking Station. [ a Thermaltake BlacX ] The drive had to be partitioned before the system would use it, and I decided to zero it too. I also chose a smaller partition than the whole drive for the system, to leave space for another system (more on this later) A few comments at this point - The Zeroing process was surprising slow. It took almost 3hrs to do a 120GB partition. I checked and the drive was indeed recognized as being connected via USB 2.0, but it's speed was nowhere near 480Mbits per second. It was more like 12MBytes per sec (96Mbits) - about 1/4 of what I expected. This same speed (or lack of it) was encountered during the "Cloning" too. The cloning process took a while, but I'm not sure how long. I performed a "Verify" on the drive to assure the copy was faithful and that it was worth testing. The system was rebooted, holding down the "Option" key and started from the 500GB drive while still USB connected. The system came up normally, and operated correctly from what I could see. The desktop showed both the new, and old system drives. After a normal shutdown, the mini was disassembled, cleaned, and the old internal drive swapped out for the new one. I transferred the foam cooling air baffle to the new drive, and reassembled the system. The unit was powered up with a PRAM reset (Command-Option-P-R) and then Option. The system indicated a single hard drive ( the new one ) as my only choice. When selected, it started normally - the only clue something had changed was the settings reset in the PRAM and the empty extra partition now showing as a new drive on my desktop. About now, you might be asking - "So What? It's just another success story... why is that so surprising, and why the thread?" That's fair. If you didn't know that I tried this unsuccessfully once before using a different USB adapter and HD while the Mini's firmware was still at 1,1 - you wouldn't think it was anything unusual. I've researched it a little since then, and some others report having problems with this upgrade path too. To be specific - last time I tried this, the Mini would not recognize there was a valid system on the cloned HD when installed "internally". (it looked empty) However, I was able to boot it and use it when installed on USB. Furthermore, I was able to do a clean install of OSX 10.4 from the original DVD to that drive when installed internally. So I know the drive was both compatible and good. Note this "Re-install" path is no longer open to me as the original DVD now thinks it's trying to be installed on a Mini 2,1 - which it was not shipped with. I've been unable to get hold of a Mini 2,1 Tiger disk or a retail Leopard disk. An "HD Clone" is my only upgrade path. I expected more problems this time, but it all went without a hitch. Thing is - I'm not sure exactly why. Hence the thread to report the facts. So what's different? The Mini's firmware is 2,1 now (was 1,1) The clone was created using a different USB adapter (docking station) The Drive itself is a different one, and of different manufacture A PRAM reset was performed (I may have done this before too - I can't recall) Interested parties will need to decide which of these did the trick. I can only say - it is possible and has now worked. (A drive Cloned via USB and then installed internally) Were I to do this again [or alot] I'd probably invest in the version of the docking station that has ALL the convenient interface types: eSATA, USB2.0, USB3.0, Firewire 400, Firewire 800 and use Firewire to attach to the Mini. Lastly, I may eventually resort to a Mini-to-Mini "Target Mode" clone session if I'm unable to obtain a suitable Leopard DVD.