If the key you press to get into the bios Setup is not displayed on the screen while booting, you may be pressing the wrong key - it can be F1, or F2, or Del, or another key or comination of keys - see your user manual.
In most cases you press the key repeatedly while booting, you don't hold it down, but in the case of some laptops what you need to do is different - see your User manual.
"If you have to use an adapter for a device, I suggest that you purchase a device that comes with it's own adapter.
'All' adapters do not work with 'all' devices."
As far as I have been able to determine, a simple USB to PS/2 adapter (female USB, male PS/2, on the adapter) is always wired up the same way BUT.....
a simple adapter that converts a USB connector on a cord so that it can be used with a PS/2 port connection will NOT work unless the keyboard or mouse is a "combo" one that was designed to be used with both types of connections - otherwise the circuits are not there in the keyboard or mouse circuits that allow that to be possible.
All "combo" mice and keyboards come with a simple adapter when new, and their label usually indicates they can be used with either type of connection.
I have never seen a setting in a bios Setup that can disable a PS/2 keyboard.
If the emachines keyboard has a PS/2 connector, it should work fine in a PS/2 port, but the wiring of a PS/2 (female) to USB (male) simple adapter varies, and a "combo" keyboard may not work with a simple adapter it did not come with.
If the emachines keyboard is really old and has the larger roundish DIN connector, a standard simple Din (female) to PS/2 (male) adapter will always work.
You CAN get a different type of adapter that has cables and circuits between the connectors that allow a USB only keyboard or mouse to be used with a PS/2 port (USB female to male PS/2), or visa versa (much more common, often USB male to two PS/2 female, for either or both a PS/2 keyboard or mouse), but it costs more than a simple adapter, though not a lot more these days.
"the BIOS doesn't have an option to change the USB Controller to BIOS as opposed to O/S."
That's not the setting for the USB keyboard. The setting that needs to be enabled in Setup if you want to be able to access the bios Setup while booting with a USB keyboard is Legacy USB, or USB keyboard, or similar. Your USB keyboard will be recognized automatically by Windows itself regardless of that setting if it is working properly, unless the USB controllers have been disabled in the bios Setup.
In older bioses that setting is often disabled by default - in newer bioses it's often enabled by default. If a USB keyboard doesn't work to get into the bios Setup, you need to use a PS/2 only keyboard, or a "combo" keyboard with a simple USB to PS/2 adapter on it, in order to get into the bios Setup and change the setting related to the USB keyboard.
....
If your laptop has no PS/2 port, there is probably no setting in the bios that disables Legacy USB or USB keyboard or similar, so a properly USB connected keyboard should always allow you to get into the bios Setup, unless the keyboard or it's connection is defective, or the USB controllers are disabled in the bios.
