Vostro 420, upgrading for gaming

The first thing, a Ryzen (or any AMD) will not work in a motherboard designed for Intel.  

Second, basically you are building a new PC.  The Vostro is sold by Dell as an entry level business machine.  Its not a gaming PC and can't really be made a "gaming" PC.  It is old technology, too.

I have to prove everyone wrong for under-estimating the Dell Vostro 420's potential. I put in an Intel Core2 Quad Q9550 (Q6600 originally, still using the stock cooler because of the screw holes, and applied decent thermal paste), added a RX570 Gaming 4gb from Gigabyte, upgraded the storage to an SU800 256gb SSD from ADATA, stuck some some random stickers onto the front from a Best Buy 2019 summer magazine, upgraded it from 3gb to DDR2 PC2-5300 8gb (4x2gb), installed Windows 10 and it's surprisingly on par with the PS4 Pro in terms of FPS in games like GTA5 (it gets 30-40+ FPS!) and a solid 40+ in the worst parts of my PS4 Minecraft city (cross-play) where the normal PS4 struggles to maintain a reasonable FPS count- remember PS4 & PS4P will target 60 FPS in Minecraft, not 30. The GPU and PSU I bought for it were intended for another PC, but I ended up repurchasing them because of how much performance I got from putting the GPU into the Vostro and my already-decent 500W PSU in it (stock one died) didn't have the 6+2 PCI-e I needed for the GPU. The C2Q will inhibit extremely good FPS in heavy titles, but the RX570 GPU will work just fine to carry it through any game at 1080p with max visuals. Expect quality, not quantity.

Total cost to upgrade it: Expect around $300-$400, possibly $450 if something's scarce like good DDR2 RAM. Some parts are used. Your mileage may vary. Any modern GPU will work, but the RX570 has a good price/performance balance as well as a good physical size- fits no problem. My main rig's GTX1080 was shoved into it with barely any room to spare- it made no difference, so don't spend more than you need to and don't buy anything longer than a GTX1080FE.

If the CPU doesn't work, upgrade to BIOS V1.3.0. I've never ran the Q9550 CPU on a lower version.

You can game on that, get a high quad core cpu (im running a q9500) and get 8gb of ram, the a gtx 960 should do wonders, i do recomend getting a new PSU regardless of what you do (semi modular at least but thats personal preference) 

the op stated games, but not expectations for speed, FPS or lag or if online multiplayer or if only single playing./

nor if willing too wick back textures not if demand playing 2k or 4k resolutions.  no idea at what is expect me.

so the answer is

yes for Yolanda.

and no for JOE.

but do folks do this sure ever see this post , by me endless(and others) and here I go again even 2time today.

almost 400 persons. (nah only 400 did, it and for sure NEVER ME on this old dog.. not ever. nor ever.

OMG CORE2. old but is cheap dirt cheap , nobody wants a CORE2, now,  they are Goodwill(tm) fodder now.