Dear Captain,
MichelPM wrote:
Your father's iMac can run OS X 10.7 Lion, though.
Whoa! He may NOT be able to run Lion 10.7. Only the last of the 2006 iMacs can run Lion due to processor limitations. Lion requires a minimum Core 2 Duo processor. Only the iMAcs that Apple names "Late 2006" have that processor. Here's how to find out:
1) From your Apple menu, do "About this Mac".
2) Look at the "Processor information" in the resulting window.
3) The processor Information must read "Core 2 Duo," not "Core Duo" to run Lion.
If you wish further verification, click on "More Info" in the "About" window. That launches System Profiler; its opening screen looks like this (example taken from a notebook but the info is in the same places):
To run Lion, the Model Identifier must have the code 'iMac5,1" or higher number to run Lion.
While there, see how much RAM is installed. Even if the processor is Lion-capable, a lot of older iMacs have very little RAM by today's standards. 2GB RAM is the bare minimum for Lion. The Late 2006 iMac can use up to 3GB RAM, still dicey.