It's an ASUS card Radeon RX 580 8 gig video memory PCIE 3.0

I figured if I got a video card that supports DX12 that Horizon Zero Dawn would at least start. But no it will not start. I double click the desktop icon and a little black hour glass briefly shows and nothing else happens. Maybe my anti-virus is blocking the game.exe. Or maybe during download of the off-line installer files maybe the antivirus decided it didn't like the files.

During install of the game, the file integrity was ok. I have the card plugged into a PCIE 2.0 mob. I've read that is only a 1 or 2 % decline in performance.

So, at present time, my system is:

500 gig SSD
1920/1080 HDMI
PCIE 2.0 mob
Asus Radeon RX 580 8 gig
AMD Phenom II X4 965 3.4 GHZ processor
12 gig gdrr3 memory

All other games installed have a noticeable improvement.

An online test says my system meets the minimum requirements. So why won't HZD even start?

You still don't meet the minimum CPU requirements. The minimum AMD CPU is from 2012, yours is from 2009 and is significantly weaker.

Minimum Processor:
Intel Core i5-2500K@3.3GHz or AMD FX 6300@3.5GHz

https://cpu.userbenchmark.com/Compare/AMD-Phenom-II-X4-965-vs-AMD-FX-6300/606vs1555

Additionally, a post on the steam forums also mention that the game won't start on the Phenom II
https://steamcommunity.com/app/1151640/discussions/0/2943620809086264998/?ctp=5#c2986413884511202761

There must be something off with that online test if it says you meet the minimum requirements!

I had a suspicion about the processor. So my next step is a pcie 3.0 mob, appropriate processor, and at least 16 gig of ddr4 ram. All this reminds me of the time the original King's Quest V on 1.4 floppies (sold at radio shack for $51) eventually cost me over $300. I had to purchase an external scuzzi drive to install the game on my Tandy 1000 pc.

Ah yes, the fun of PC Gaming!

King's quest V was such a great game, I had it on the the 5.25 inch floppies for MS-DOS myself. Hey, at least you got to experience the version of KQ5 without the terrible CD voice acting! (It's available on GOG if you REALLY want to try it)

I remember picking up Ultima IX on sale for $20. Then realizing it really only ran well with 3DFX Glide, picked up a heavily discounted Voodoo 5 for $200 to play it.
I was expecting a speed upgrade for my machine, but the irony was that the Voodoo 5 had worse 2D and Direct 3D performance than my cheaper ATI card that I had previously installed.

While I'm thinking of it, you are running a 64-bit version of Windows 10, correct? HZD requires that as well.
And while technically not required, you'll want to run the game off a SSD.

Finally able to play HZD on a borrowed PC similar to mine except the second PC has the Ryzen I5 processor and some decent ram. I downloaded and installed the special video drivers for HZD. Game is flawless and very sharp resolution.

How are you liking it? I seem to remember you've been trying to get it to run for some time.

I hope you're enjoying yourself. Also the 580 is a really nice card, congrats.

I suspect that some main quests are only available when you do certain side quests. I've gotten pretty far and all of a sudden hit a hold up and can't seem to progress. So in the meantime, I managed to get into the far northeast where near where the DLC takes place. The Tall Neck there is destroyed and covered with snow and ice. Is this intentional because the Tall Neck is related to the DLC!?

Anyway, I've got lots of time and can retry some areas to see what's what.

Yes, that Tall Neck is a side-quest which is gated by another side-quest (not main quest).

I don't know if there is an alternative way to get that Tall Neck's quest other than the "gatekeeper" side-quest.

Now for the nasty part: I want to try getting the golden travel pack so that never runs out. Only thing is, the most recent version of the game doesn't agree with the latest version of HZD cheat table. All I see is version 1.5.which is much to low for the latest game version.

*****

Found updated cheat table, except it has no option to search for an item name as far as I know.