To upgrade you need to be sure your model meets the requirements:

1. Intel Core 2 Duo Processors
2. Macbook Pro Core 2 Duo
3. Mac Os Sierra Intel Core 2 Duo

• Mac OS version: Metal required. MacOS X 10.11 (El Capitan) Processor: Intel Core 2 Duo 2.4GHz Processor or better; Memory (RAM): At least 4 GB RAM; Hard drive (free space): At least 15 GB of free space with at least 1 GB additional space for custom content and saved games. Graphics card (video): NVIDIA GeForce 9600M GT, ATI Radeon HD 2600 Pro.
• Per Apple's TN: System requirements for OS X Mountain Lion. 'MacBook (Late 2008 Aluminum, or Early 2009 or newer)' is supported. Your system: Apple MacBook 'Core 2 Duo' 2.4 13' Early 2008 (White or Black) as listed in EveryMac. Sadly, the answer is No you are now running the highest OS this system can support (10.7.x aka: Lion).

However, the iMac 'Core Duo' 2.0 20-Inch replaces the PowerPC G5 processor with an Intel 'Core Duo' processor, which makes it a member of the the first desktop Mac series to be powered by Intel. This model features a 2.0 GHz Intel 'Core Duo' processor (T2500), with two independent processor 'cores' on a single silicon chip, a 2 MB shared level.

Upgrading to El Capitan

You can upgrade to El Capitan from Lion or directly from Snow Leopard. El Capitan can be downloaded from the Mac App Store for FREE.

To upgrade to El Capitan you must have Snow Leopard 10.6.8 or Lion installed. Download El Capitan from the App Store. Sign in using your Apple ID. El Capitan is free. The file is quite large, over 5 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.

Macs that can be upgraded to OS X El Capitan

1. iMac (Mid 2007 or newer) - Model Identifier 7,1 or later

2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) - Model Identifier 5,1 or later

3. MacBook Pro (Mid/Late 2007 or newer) - Model Identifier 3,1 or later

4. MacBook Air (Late 2008 or newer) - Model Identifier 2,1 or later

5. Mac mini (Early 2009 or newer) - Model Identifier 3,1 or later

6. Mac Pro (Early 2008 or newer) - Model Identifier 3,1 or later

7. Xserve (Early 2009) - Model Identifier 3,1 or later

To find the model identifier open System Information in the Utilities folder. It's displayed in the panel on the right. See the following User Tip: Basic Steps for Upgrading OS X.

Are my applications compatible?

See App Compatibility Table - RoaringApps

Apr 7, 2016 1:11 PM

About This iMac

The Apple iMac Intel Aluminum “Core 2 Duo” computer released August 2008 was another creative step in the evolution of the iMac. The new aluminum bodies certainly became a stand-out highlight however the external design was not the only fascinating thing this device displayed. It also had a faster processor under the body, the Intel “Core 2 Duo” processor and the ATI Radeon HD 2400 XT with graphics acceleration for graphics. The FireWire ports were still limited to 2 ports however, the second FireWire “400” port was upgraded to a FireWire “800” port. The design of this iMac oozed elegance and class and in some circles is still a very useful machine.

Storage

The device was built with 250.0 GB Serial ATA (3Gb/s) hard drive storage with a disk speed of 7200 RPM.

Intel Core 2 Duo Processors

Screen Size and Resolution

Macbook Pro Core 2 Duo

The iMac Intel Aluminum “Core 2 Duo ”featured a 20 inch screen with “glossy” TFT active matrix LCD display and a native resolution of 1680×1050.

Inclusive Features

The iMac includes the following features and ports:

• A Power Adapter (100V-240V AC, 200 W maximum)
• Standard AirPort Extreme (802.11a/b/g/n).
• Gigabit Ethernet
• One FireWire 400 port
• One FireWire 800 port
• 8X DL “Super Drive”
• 1 Mini-DVI that supports both mirroring and extension.
• Built-in Stereo Speakers

Mac Os Sierra Intel Core 2 Duo

Processor & Graphics Processing Unit (GPU)

The iMac Intel Aluminum “Core 2 Duo” had the Mac OS X 10.5.2 (9C2028) operating system pre-installed on it. It was powered by a 2.4 GHz Intel Core 2 Duo (E8135) processor. Its graphics processor was the ATI Radeon HD 2400 XT graphics processor — using PCI Express — with 128 MB of GDDR3 video memory.

Memory & Architecture

The device was built with 6 MB on-chip level 2 cache with a frontside bus of 1066 MHz and with 1 GB of 800 MHz PC2-6400 DDR2 SDRAM for its RAM. It’s designed was centered on a 64-Bit architecture.

Upgradability

Although the iMac Intel Aluminum “Core 2 Duo” came with 1 GB of RAM, it could be upgraded up to 6 GB of RAM.

The Operating System of the iMac can also be upgraded from its pre-installed Mac OS X 10.5.2 (9C2028) up to MacOS X 10.11. This iMac was also able to act as a host Windows OS, mainly being Windows XP SP2 (32-Bit) and more recently Windows 7 (32-Bit).

This iMac Intel Aluminum “Core 2 Duo” had the following dimensions of 46.9 cm, 48.5 cm, 18.9 cm and a weight of 20 lbs (9.1 kg).