how can i determine what the most recent os my imac will run?

Snow Leopard General requirements

• Mac computer with an Intel processor
• 1GB of memory
• 5GB of available disk space
• DVD drive for installation
• Some features require a compatible Internet service provider; fees may apply.
• Some features require Apple’s MobileMe service; fees and terms apply.

Lion System Requirements

• Mac computer with an Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
• 2GB of memory
• OS X v10.6.6 or later (v10.6.8 recommended)
• 7GB of available space
• Some features require an Apple ID; terms apply.

It's not usually a good idea to post your serial number in a public forum. If you are able to edit the post I suggest removing it.

Based on the infomation you provided you have an iMac (20-inch Late 2006) system. According to the Lion specifications available at http://www.apple.com/macosx/how-to-buy/ you need at least an Intel Core 2 Duo processor which you have. One concern I have is that your system may have a limited amount of memory which could really slow down the performance of your system when running Lion. If you want to upgrade to Lion I suggest maxing out the memory which according to http://support.apple.com/kb/HT2821 is 3GB.

You CAN run 10.7, but I don't advise it, buy the 10.6.3 upgrade disk from the Apple Store online and then backup files off the machine and upgrade to 10.6.3., then Software Update to 10.6.8 would be the BEST option for your older hardware and it will run most all of your 10.5 software and be faster than 10.5 or 10.7.

If you go to 10.7 it won't run nearly any of your 10.5 software and you will have to buy all new ones for a machine that's getting a little bit dated, near it's end of life stage. 10.7 will slow your machine down, especially with low RAM.

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At your machines stage, the hard drive is getting old, the vents are clogged up with dust and it's going to cost a bit to get the drive etc upgraded. You can if you wish, but 10.7 really needs more RAM (4GB) and a faster hard drive.

But your still subjected to the video card going out etc.

IMO upgrade to 10.6.8 and stay there until the wheels fall off, then buy a new 10.8 machine being released after this summer or 10.9 machine. 🙂

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