When upgrading from 4GB to 8GB the system beeps.

"Are you using a matched pair or a mix and match set? Mix and matches can be made to work, but you need to make sure your specs are similar or the same; brand (usually) doesn’t matter. The problem with mixing most OEM modules is most prebuilts use the cheapest junk they can get with high latency, so you need to get equally as junky modules to stand a chance. Since the CL ratings are generally way off between any retail module worth selling and OEM (retail fails), it usually doesn’t work unless you get lucky. You generally need to find the exact same module or a similar module to make it work, and even then it tends to have stability issues unless it’s a near perfect match. This is why we don’t do it in a professional setting - it takes way too long to make it work.

The other issue is HP hardware is not receptive to mixed factory and retail modules a lot of the time - you genuinely need the matched kit unless you buy the OEM spec modules with a lot of them. Sometimes it works but I’ve seen more HPs have touchy memory compatibility, on par with Apple.

What I would do is buy a 16GB 2X8GB kit from Crucial or Corsair and do a matched pair upgrade - this machine supports 16GB natively, so it isn’t a problem. Even if it didn’t, it doesn’t tend to be an issue as long as the PCH supports it and the BIOS isn’t artificially limited. It doesn’t cost much more to get a 16GB set, which will put you in a better position long term over the 8GB option. Having a 2 DIMM board puts you in a poor position since you can’t buy a 2X4GB kit now and get an exact match to what was installed later - if they even still sell it. The i3-6100 technically supports 64GB, but your 2 DIMM board really limits you to 32GB unless you can find a 2X32GB kit if you ever wanted to try it.

Best to install 16GB now and get it over with since it’s going to be more expensive then a 4 DIMM board due to the need for high density RAM."