Sure you can make a slave drive bootable...but whether you can use it is a whole different thing.

Slave is kind of a misnomer. In computing terms all it really means is another drive attached to the same cable plugged into the same controller. It is actually more on the terms of primary/secondary than master/slave. but since there were normally two controllers ...primary and secondary... the master/slave aspect took over. so in reallity it is primary controller with primary(master) and secondary (slave) devices and then secondary contoller with primary (master) and secondary (slave) devices...see the confusion LOL

The controller found and used the devices as to which connector they were plugged into on the cable starting with the end connector (primary/master) or the middle connector (secondary/slave) and so it goes that it was too slow and came up with a better/faster proccess to do the job...SATA in which all devices connected are primary/masters.

Getting back to my original statement...if the slaved drive is USB connected then the answer is yes it can be made as bootable but only if the motherboard supports the booting from a USB external port. If it doesn't then the USB slave cannot be made bootable. (actually it still can but the boot aspect would be useless)If it is internal then yes it can be made bootable...within protocols....windows will only allow 4 bootable devices period...it is a fixed thing within windows boot management program.

If it is Esata connected then it is not a slave drive but a master drive and can be made bootable but again only up to four bootable drives per operating system.

The way to get around the 4 bootable drives is by using a third party boot manager that hides the boot records.

Hope that helps answer your question!