Hi cortez1way, Welcome to THW.
Most likely your system memory(Your CPU has really no relation to it) is not HP, they do not make PC memory they use other companies and just install it into their computers.
That said you usally want to buy the same exact brand and model specs of memory when you want to add more to you PC. That means if you cannot get the same brand memory you at least want to get the same speed, latencies, and voltage. All these specs are provided or should be where ever you want to buy the RAM from.
If you can give use the exact model of your PC and the motherboard, we will be able to help you further.