The graphics card will be too slow for anything but early XP era games, say up to 2003. Especially if you're gaming at anything above 1280 *1024 resolution. The CPU is hot, loud but plenty fast enough for the early XP era games; the graphics card is the bottleneck. It won't hold up for later XP games (e.g. Oblivion). You're a bit stuck there because if you want to you want a faster graphics card you're stuck with AGP cards on that system. Fast AGP cards are expensive and still "not that fast".
It sounds to me that you're more interested in playing the games than picking up "interesting" or rare hardware. Good news, you can save yourself a ton of cash!
My suggestion would be to go for the next generation socket (Socket 775) up from yours (Socket 478). You can get a basic Core 2 Duo CPU, say an E8200 or E8400, and it will be much faster and quieter than your Pentium 4. Socket 775 allows for both DDR2 or 3, depending on what motherboard and chipset you get (I'd suggest a G41 based board because it is cheap and has the DD3 Support). For the graphics card you can put just about any PCI-E graphics card in there and it'll be much faster than a reasonably priced AGP card.
I'm bored so I picked out a bunch of parts for what I would go for (although you're probably not in the UK!)
£18 motherboard (DDR3) - nothing amazing but quite adequate.
E8400 CPU £3.
2x 1GB DDR3 £5
Now for the graphics card, you could go cheap, low power but not very fast like this Radeon 4670 (for comparison an AGP one is on sale for £109!)
Something cheap, definitely not low power, but fairly fast for xp you could go for something like a Nvidia 275
For something reasonably priced and very fast how about a 560ti
This PC would be plenty fast enough for all XP era games (that is, games that aren't on steam or GOG or whatever that work on Windows 7 / 8 / 10). Of course, you could have a lot of fun playing early XP games with the PC you linked a picture of too.
Ryzen 3700X | 16GB 3600MHz RAM | AMD 6800XT | 2Tb NVME SSD | Windows 10
AMD DX2-80 | 16MB RAM | STB LIghtspeed 128 | AWE32 CT3910
I have a vacancy for a main Windows 98 PC