What do I do after get DISK BOOT FAILURE on my monitor?

[Linnaeus]

I'm doing an external build instead of putting all the components in the case. What do I do after I get the message DISK BOOT FAILURE on my monitor? I don't want to install the OS yet since the components aren't in the case yet. How exactly do I turn off the external build?Can I just switch the PSU to off and then begin to take apart the PSU connectors ?

 

[ss202sl]

Yes. Just turn the power switch off.