In most cases, memory is not the cause of a PC running slow. Extra memory can mean more programs open at one time but it doesn't really speed up the PC.
I couldn't find the spec's on the HP site documents for this specific PC.
Windows 10 64 bitIntel i7 6700K16GB Corsair DominatorIntel CPU Graphics
Computer type
PC/Desktop
Computer Manufacturer/Model Number
My Own Build
OS
Windows 10 64 bit
CPU
Intel i7 6700K
Motherboard
ASUS ROG Maximus VIII Hero
Memory
16GB Corsair Dominator
Graphics Card(s)
Intel CPU Graphics
Sound Card
RealTek
Monitor(s) Displays
27" Dell S2719dgf
Screen Resolution
2560X1440
Hard Drives
1 TB Samsung 850 EVO SSD for Win 10 Pro
500GB Samsung 850 EVO SSD for Win 10 Insider
2 TB drive for backup
PSU
EVGA Supernova 750G2
Case
BeQuiet Silent Base 600
Cooling
Deepcool Captain 120EX
Keyboard
Microsoft Wireless 2000
Mouse
Microsoft wireless
Internet Speed
100 MB/sec (Cable)
Antivirus
Microsoft Defender and Malwarebytes
Browser
Edge/Firefox
Other Info
Cakewalk (Sonar) by BandLab and Studio One 4.1 Pro recording studio software. MOTU 896Mk3 Hybrid recording interface, Frontier Tranzport wireless control unit, Behringer X-Touch Control Surface.
Five USB connected optical drives for CD Audio production using Nero BurningROM
Adding RAM certainly can improve performance but there is always a point of diminishing returns after which there will be little gain. With typical workloads you are probably beyond that point with 4 GB RAM. If the computer worked well with Windows 7 then is seems likely that something is wrong and needs to be investigated. Windows 10 memory requirements are generally somewhat lower than for Windows 7.
My Computer
At a glance
Windows 7 Pro 64 bitXeon W35208 GBNvidia Geforce 210
You can add 1600 MHz if the motherboard supports that speed, but even if it does it will still only run at 1333 because you already have that installed and the memory will always run at the slowest speed installed.
If the MB supports 1600 MHz then you should install all 1600 MHz speed memory.
Please post a manufacturers link to your motherboard, Thank You.
If you find that you actually like Windows 10, you can now do what we call a clean install of Windows 10, it will activate, and all your slowness should dissapear.
Let us know if you`re interested in doing that.
If not, you should just go back to Windows 7
Without knowing what exact motherboard you have, we can not advise you efficiently
My Computer
At a glance
Windows 10 Pro x64Intel Core i7 6700KGSkill TridentZ RGB 16GB 3600 16-16-16-36EVGA GTX 980 Ti SC x2
First of all do not exlude the posts from the others before my posts. These people have been on this site for a long time and are much more versed than me. Its just that I went through a 7 to 10 upgrade recently and found out things I was unaware of and thought I would share them. I checked the HP website and it indicates that your laptop has not been tested for Windows 10. They do not have drivers for Windows 10 available. This may be why its slow, I'm not sure. I ran into an issue with a Lenovo that the "Get Windows 10" utility said it was compatible but Lenovo did not have drivers for 10 yet. Some older laptops may not be compatible with 10.
A laptop could have limited bios access and settings and also limited drivers availability from the manufacture.
This makes updating to W-10 a iffy thing to try in my opinion.
My Computer
At a glance
Windows 10 Pro. 64/ version 1709 Windows 7 Pr...Intel i7-6800K @ 4.3Corsair Platinum 16 gig @2400EVGA GTX 1070 OC
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Home made Desktop
OS
Windows 10 Pro. 64/ version 1709 Windows 7 Pro/64
CPU
Intel i7-6800K @ 4.3
Motherboard
ASUS X-99 Deluxe II
Memory
Corsair Platinum 16 gig @2400
Graphics Card(s)
EVGA GTX 1070 OC
Monitor(s) Displays
Asus 27" LED LCD/VE278Q
Screen Resolution
1920-1080 or 1280-720 HDMI
Hard Drives
INTEL SSD 730-240 Gb Sata 3.0/
PSU
EVGA Platium 1200W
Case
Phanteks Luxe Tempered Glass 8 fans/ one radiator
Cooling
XSPC/ Water Cooled CPU
Keyboard
Das 4 Professional
Mouse
Logitech M705/MX Anywhere 2-S
Internet Speed
100 mbits
Antivirus
Microsoft Security Essentials/ Malwarebytes Premium 3.0/ SAS
Browser
I.E. 11 default/Firefox/ ISP Time Warner Cable/Spectrum
Other Info
LG BluRay Burner/
Sound system-KLipsch-THX/
Icy Dock ssd Hot Swap bays.