XPS One A2420, upgrades RAM, SSD, CPU?

The Setup Guide say 2x 2 GB RAM max, dual channel 800 MHz DDR2. Doesn't necessarily mean more won't work, but 4 GB is all that Dell validated in this model. And 4GB is too little to run Win 10, which is the only OS that's currently supported by Microsoft.

What CPU do you have now?

Is it worth putting money into this old PC?

4 GB DDR2 is costly because it is rare. Standard ddr2 is typically 1-2 gB per stick.

I had installed Win 10 in old optiplex Dell pc running c2d and 4 gb. Install was fine. One client said when using Firefox he preferred to have 8 gb to have a low % memory usage. With 4 gb he got 80% or more memory used during browsing. 

If I upgrade my a2420 from the Q8200 to the Q9650, will the system fans spin louder? Or is the Q9400 the best option without getting this problem?  The bios is updated to the latest version of 1.1.4.  I've also noted that most people that had this problem usually had the XPS one a2010 and to remedy the problem they used good thermal or some just go back to the old CPU. I just needed to be sure before I make any other choices.

What operating system did your computer ship with?  As I understand it, 4GB was the limit for a 32-bit OS.

I'm currently repurposing my 2007 (not Dell) computer that was replaced by a Dell XPS 8900 when it stopped booting up.  The old computer has an Intel E6600 Core 2 Duo processor and came with 2GB (2x1GB) of DDR2 and 32-bit Windows Vista.  I'd upgraded the memory to 4GB (4x1GB) and had replaced the graphics card and PSU before it became redundant.  The computer has sat idle for the last five or six years.  After , blowing and brushing out the accumulated dust and replacing the coin battery, I booted the computer into BIOS and have since put a clean install of Linux Mint 20.1 on a new SSD.  I've upgraded the memory to 8GB (4x2GB) DDR2 bought cheaply on eBay and will soon be fitting an Intel Q6600 Core 2 Quad SLACR (also bought second hand) and a new cooler.  I wish I could use a Q9XXX series Core 2 Quad, but my old motherboard doesn't support them.

The Q6600 actually was well known for overclocking back then.  You could do a tape mod (BSEL) and pushing it to 3 GHz using stock fan, very stable. 

I've got an nForce 680i SLI Motherboard with excellent overclocking potential in the BIOS, so I'll probably see where I can push it to.

It was given to me from a friend of mine who ordered it fully loaded and maxed out for the time. It had windows vista ultimate 32 bit with 4GB of ram with the 8200 cpu. It had all the media accessories that was available at the time like the remote control, the keyboard with the mouse/remote combo, RCA plug connections with infrared port, and the Internal tv tuner. It was later updated to windows 7 ultimate 32bit.  He stopped using it because at the time, there was video driver issue with intel and nvidia that was going on with the display going black after updates. Then a year or 2 later, the upper half of the screen was very cloudy. We thought it was adhesives behind the screen itself was getting loose. He gave it to me some years later and I took it apart a few months ago found out it's only dust that got blown between the glass and screen itself, after I realized Dell didn't design this model in such a fashion or used that method at that time.

What I'm planning on doing is upgrade the RAM to 8GB, CPU to a 3GB quad core, and a large enough SSD to dual boot it with windows 10 and a linux OS or ubuntu. Also I want to take advantage of the media capabilities of the system so I'm planning on having this as my office and dvr system which I know are ways to still use it in that way without microsoft media center. And upgrade the ODD to a blu ray burner if possible as it have a dvd burner on it now.

But the question I do have, what brand RAM you have that works? Currently I have a pair a hynix (2x2GB) that was originally shipped with the system. I brought a pair of Samsung PC-6400U-666 DDR2 sticks from Ebay back in January. Everything is in the exact specs that should boot. On ebay they say it's only for a AMD motherboard but if this is DDR 3 and 4 that won't matter as long the specs are right for the motherboard. I forgot in DDR2 standards, it does. I do have a Q6600 that came a XPS 410 that's given to me. Right now, its in a Dimension E520. I could switch if the E520 can used the Q8200. So I could do that as long as the 2420 fans run normally and quiet. The cheapest RAM I've seen on Ebay is a set of Patriots that's says is made for intel but its 79 bucks.

The memory that I've purchased recently is Elixir M2Y2G64TU8HD5B-AC (4 sticks of 2GB).  Prices must be different in US, as the 4 sticks have cost me £13.60 total, used on eBay.  Before this, I had a mixture of Elixir and Kingston 1GB sticks.

A few questions:
Do you have 4 RAM slots?
What chipset is on the motherboard?  I'm limited to E6X00 & E8X00 Core 2 Duo and Q6X00 Core 2 Quad processors due to the nForce 6 series chipset.

I do have a Q6600 that's in a Dimension E520. With this in mind, I could switch CPUs if the dimension can use the Q8200 from XPS One. I've seen the BSEL mod before, but wasn't sure about it with stock cooling fans on my XPS 410 when it was using that CPU. Right now it's using a Q6700. But this is a better idea since I already have these processors than buying a Q9650 or 9400 for the XPS one.

The 4 sticks of 2 GB sticks are rather cheap in the U.S. markets as well. Especially in my older machines that have 4 slots.  The only machine of mine that don't have any RAM and planning to build up is a custom case built system with a Dell 8900 motherboard which uses a i7-6400k CPU and DDR4 RAM.  Everything else is just stock case systems, with upgrades.

This project is a XPS One a2420. It's a all in one system so only upgrades are only in CPU, HDD, and RAM. Wish I can upgrade the motherboard but all in one systems are like laptops and only built for that certain board. And because of this,  it only has 2 slots for DDR2 RAM and that will cost a lot more as  mentioned in this discussion by user redxps630. DDR2 memory with 4 GB of memory on each stick is more expensive as that amount of that type of sticks are rare and was produced later. If it was made earlier,  I'm certain this machine would had it shipped. The chipset this board uses is a Intel G45/43. According to cpu-upgrade.com this chipset combo has a range from intel celeron,  celeron and intel duo, and quad core duos of Q6xxx to Q9xxx and the extreme QX9650.  This system I've seen come with certain intel duos and the Q8200 on quad. I'm not certain about its 20 inch a2010 brother, but I'm certain its similar. The question I was looking into is upgrading a 3GB cpu make the fans run louder and run stable and the brand of RAM used since on ebay if they say a DDR2 memory is made for AMD,  it means it.  I'm planning on using this machine with certain tasks as certain people successfully made the same upgrades but not saying what are the conditions after the fact or brand of memory.

But your motherboard is a 680i SLI, here is what cpu upgrade says here. But for quads I only see is Q6600 and 6700 to be compatible. But I know are solid processors and the BSEL mod can do the trick as mentioned. But this site could tell you a bit more information you're looking for.

https://www.cpu-upgrade.com/mb-Intel_(chipsets)/P31_Express.html

Re:  The question I was looking into is upgrading a 3GB cpu make the fans run louder and run stable and the brand of RAM used

@Antaries7, @Jon-62 . There are variant of overclocking for the Intel Q6600.  Before working on your mod, review how others working on theirs.  I'd done twice a while back with 2 different methods.  One with tape over 2 pins and the other was connected 2 pins with electrical pen.  They were both done on Dell Inspiron with stock fan, stock rams, and BIOS with zero option for overclocking.  Both systems were stable and produced around 30% increase in performances.  Temps were around 3 degree warmer than before mod.  Therefore no increase in fan noise while idle.  However, one system had a faulty chipset sensor, which reported 85 degree at all times. 

If you plan to work on yours, be sure to record all conditions prior for comparison, the tape mod is reversible so if your system become unstable, just take the tape out.  The Q6600 will be stable at 3 GHz, go over that, it will be crashed under load.

In my opinion, repurpose or upgrading your system should depend on situation of each person, some do it to salvage old parts to make use of, others are enthusiast wanting to satisfy their abilities.  The cost should be consider for the value of end product and your time.  With about one hundred USD, you can get a Dell business machine (Optiplex) with Haswell processor, 8 GB of ram, 256 GB SSD, onboard graphics with ability of 4K display.

I hope some of the information could help you with your quest.