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OSX has been around since 2001.
OS9 was there till late 2000.

If you are talking about the new 10.8 ML, we don't know.
But with late 2007 MBP, Lion lags a bit compared to one's with i5/i7s.

We will know soon for the specs but it might be heavy.
I prefer you get a SSD and more RAM.
 
You can do Lion but half your memory could theoretically be tied into the system itself as it seems Lion is a little more memory heavy that previous OS X versions. If you already are maxing the 4GB of RAM with what you do, getting 8 GB (which I believe your system supports) for $35-45 is well worth it IMO.
 
You can do Lion but half your memory could theoretically be tied into the system itself as it seems Lion is a little more memory heavy that previous OS X versions. If you already are maxing the 4GB of RAM with what you do, getting 8 GB (which I believe your system supports) for $35-45 is well worth it IMO.

His system only support up to 6GB, 1x4 and 1x2. Not 8, it will not even boot with 8 installed.

He can run Lion okay on it, I wouldn't expect Mountain Lion to perform as well.
 
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