I know NVidia better than ATI, so I'll give you some advice or links etc.
AGP 1.0 slots, yes I remember those! FYI I've had a Geforce FX 5200 working fine in one of them. They are reasonably cheap to obtain now if you want to buy new (somewhere around the ?25 mark, I think). I also think that any of the FX 5xxx range will work ok, too, but don't quote me on that.
In my opinion, you won't extend the performance of the PC by installing a card much faster than a Geforce 4, because the AGP slot will become a bottleneck, and presumably your processor isn't particularly fast by today's standards, negating any benefit from a super-duper graphics card?
So, your best bet would be to get a 2nd hand AGP card off Ebay such as a Geforce 4 MX card or something. Whilst the Radeon 9200 would be marginally quicker, I'm not sure why the drivers didn't install, I take it you did try the official drivers from ATI?
Drivers for Radeon 9200 on
this pageSpecific driver-only package for the Radeon 9200 is
here (Direct link - 12MB)
As for NVidia cards - there's a Geforce 2 MX with 32MB of RAM
here on Ebay - ?7.99 + ?2.49 postage - it will be a lot better than what you've got in there.
Looking around again, even better would be
this one which is a Geforce 4 MX 440 card, will work fine (i've had one of these working fine in an old AGP slot, and they do make windows feel a lot more snappy, and they do play some games)
If you want to keep an eye on
this, it's an FX5200 card with 128MB of memory, currently at ?0.99 with 10 hours to go. Marginally faster than the MX440, but not by much.
Any of those ones should work in your motherboard
The only other alternative, as roseway said, is to get a PCI card, but I don't think you need to do that.