We received one of the Toshiba L855 models in to the shop for depot repair. It needed a virus scan and the OS was infected pretty badly, running very slow.
It was difficult to find any pages about how to boot a toshiba L855 S5405 to CD, but eventually we found it. The procedure to boot the laptop from a CD is to hold the F12 button and then press the power button. Continue to hold the F12 button to boot a toshiba L855-S5405 to CD and you’ll be in business in no time. You can boot and get working on the filesystem or get rid of viruses. Whatever the problem, we can help you! Don’t hesitate to call.
Hope this helps someone out there.