Will an imac reinstall OSX from the external DVD drive?

My internal drive wore out and I have been using an external. Well the OS has become crashy. I was wondering about reinstalling OSX. The computer boot from my USB external drive Do I do anything special to do this?

As long as your machine has an Intel processor, it should be able to boot from a USB device including an external DVD drive. Just hold down the Option key during the boot cycle, you should be able to see the DVD drive with your install DVD inserted. If you have an older PPC machine, the drive would have to be Firewire.

Regards.