Hi i am trying to install OS X El Capitan on iMac 2008 model Core 2 Duo processor, and 4GB Ram. The way i followed is i created a USB bootable stick and insert to mac machine and restarted the Machine then i pressed C key in keyboard and i waited more than 30 seconds then it is not showing any usb Bootable option and later it booted directly. Even i can`t able to Boot CD Drive also. can any one help me out here please.
Holding CMD + C will not boot of an USB, only a DVD.
You need to hold the option key then select the USB Drive, which will be most-likely named EFI. Also make sure you aren’t plugging it in through any USB hubs and just directly into the computer.
Note: If your able to install El Captain on your computer, doesn’t mean it will run well. Because of its age it can possibly be very laggy and be very hard to use, personally I’d recommend at max using Yosemite.