The D510 has been mentioned here a few times and Uxbill has a good video on youtube about them. What makes them a bit more interesting is they were the last true Compaq designed PC's
Mine both are early enough to have Compaq not HP badging, one even has a Compaq rather then a HP serial number, yet both have HP Windows COA stickers.

History of my PC's
I got them in 2007 when they were decommissioned from a client. 2007 when the IT budget had money to burn.
2007 was a funny year in IT, things had kind of stagnated. Windows Vista was out but flopped so people were hanging onto WinXP PC's. Exchange 2007 (which they also upgraded) was out but still needed Windows 2003, and people were still happy with Office 2003. This was all before financial crisis in 2008 so funds were healthy and companies wanted to reinvest I'm themselves.

Looking around and seeing everything was ticking along nicely I figured I'd start standardising the PC's and drew a line at 2.8Ghz which flited out about 10 PC's out of about 60.
That still left about another 15 faster D510's as well as similar spec tower versions, and really the ones been replaced were fine anyway.

1 or 2 went to staff, and I also grabbed 2 for myself. This was when I was traveling a lot so wanted a PC to backup all my files off the laptop, and the other was to be my daily driver.
and this is how it remained for the next 6 years or so, the Small Form Factor was a godsend with many house moves during that time.
Come 2012 and things were finally changing. Flash was taking over the internet and killing off single core PC's in doing so. Plus I started to get the itch to play Need for Speed 4, so the daily driver was demoted to Win9x Gaming PC, and then my downward spiral led me to getting more and more better suited PC's and yet again one and then the "server" were surplus and were put aside.

They had a brief revival last year as a office PC for my wife's business. she needed a light office work PC so installed lubuntu on both figuring I could just swap out the whole PC if it stopped working.
It was here the ram and CPU on both were maxed out. I don't think it got used that much and the business is now closed so again they went to storage.

So what's the story now?
I've grown attached to these 2 little workhorses and came up with an idea to give them a meaning in life again. 2 exactly the same LAN gaming PC's!
I had to swap out a 20GB HDD for a exact same model 40GB drive as the other (the HDD's have been swapped out for other projects so often I have no idea if any were the original anyway)
The on board graphics isn't amazing, but should be fine for the 2D RTS games they will primarily be for.

Windows XP is for Command and Conquer's by far the most played game round here and the unofficial patch while breaking Win9x support adds so much more its worth it. Also the Age of Empires series and Warcraft 2 BNE, Diablo 1 and 2
Win98SE will mainly be for dos games, Doom's Duke3d, Warcraft.
Sadly the on board sound doesn't play any music in Dos games 🙁 Adlib, FM, Midi, nothing. Oh well, It'll be in a room with others playing the game no doubt, and probably sounds terrible with the inbuilt speaker which is pretty handy as well.

I could find a couple of 1/2 height AGP cards and something like a SB Live and have a pretty decent gamming PC, but really I don't see these getting much use to justify the cost, but having a backup PC when an old mate drops round is a nice luxury. In theory I could get a 6 player Win9x network going, (if they were all working, which is rare) 7 if someone came with a screen.

But really I like the idea of having a level playing field.

and Finally specs of the PC's
Originally they came as the below although have been though many hardware changes in my time.
Compaq S/N PC
CPU P4 2.4GH
RAM: 256 MB
HDD: 40GB

HP S/N PC
CPU: P4 2.5
RAM: 128MB
HDD: 20GB

Now Both have
CPU: 3.06GHZ SL6S5
RAM: 2x 1GB PC2100
HDD: Maxor Fireball 3 40GB (Only matching IDE drives I had)

The only difference is one has a DVD-RW and the other has a CD-ROM. Again no idea which one came with which as when I had to swap the DVD drive into each when I needed to access the lubuntu DVD.

The Compaq S/N on the left in Win98, HP S/N on the right in XP showing the installed games
Also see how the XP sticker has gotten smaller?

Topless twins 😉