No need to panic as you will have just crashed your PC by putting in the second RAM stick that is not compatible with your existing one.
You need to reset your BIOS.
Read your motherboard manual or find one online if you don't have to see how to do this.
It is just a case of shorting 2 pins on the motherboard which will be labelled either Clear Cmos or RTCRST.
You short the pins with a small screwdriver with the PC unplugged from the wall of course!
Alternatively it might have 3 little pins and a jumper which is in place over 2 of the pins you remove the jumper and slide over 2 of the remaing pins then back to where it was.
If this sounds baffling then just youtube how to reset CMOS using jumper.
Another way is to take the litte battery out for 10 seconds.
Once you have reset it boot it up with only the 1 stick of RAM you had originally.
More than 1 stick of RAM has to be identical ones from the same manufacturer and exact specification.
When ordering just get 2 X RAM sticks of the exact same model instead of 2 from different manufacturers or slightly different types like you have now.
Some motherboards are less fussy and will boot with RAM from different manufacturers but seems not in your case.
They also need to be inserted into the correct slots.
If your motherboard has 2 slots then just put them in.
If it has 4 slots then consult your manual in the Memory configuration section.
Usually it's A2 & B2 slots or A1 & B1 if you don't have the manual or cannot find it online.
Andy
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