512 megs of RAM on the video card, that's still fine today.
Dimensions wise, look at that picture of the motherboard, and see the end of it on the right side, has a weird looking thing at the bottom that is the end stop on the card, for getting it locked and unlocked into the slot...
You can judge the overage of the card by how much MORE there is off it passed the part that goes into the slot, if you follow me.
That card you mention, has a 400W PSU requirement it looks like, and I doubt your PC has that, but it should be listed right on your current one in plain english hopefully, PSU wise, you could upgrade that too, just make sure you have the size on that one explicitly because those can vary so widely.
Just FYI: Video card series wise, first # is series, 2nd # is main tier, 3rd sub tier, and last if it exists is zero, lol. and higher is better and it's massively confusing to consumers and I wish they'd stop it, because you can go back 2 series and have a better card then a low one on the current series and worse.
Oh yeah and then you have GS, GT, XT, GTS, GTX which also can vary, but GTX has top dog status?
Like that 8400GS you mentioned, 8 series, but 4 makes it a sad low quality card.
My old PC has a 5900XT in it and it might give that 8400 a run for it.
I know the 5900XT is way better than the el cheapo 6200 anything, of course drivers and direct-x support also comes into play.... confused yet?
And Fumz, I agree RAM first is a must and there is a lot of close quarters issues too depending on how thick that case of his is, your right I goofed on the heat sink getting in the way, I almost confused this issue with one I was working on before it about a video card issue. My brain needs rebooting, thanks for reminder.
...and Yes that 5570 would fit, it almost stops after the slot, definitely a short enough card.