bad performance with new radeon x800xl. help please

I just bought a radeon x800xl. The frames per second in my games is much lower than what I expected from looking at benchmarks of the card online. I expected lower performance because my processor is older, but I not 50% worse in some games.

I have a 4x agp slot and for some reason in catalyst both fast write and agp write are disabled. When enabled and prompted to restart it reverts back to disabled. Some people have said it makes no difference and another person told me they got a 30% gain by enabling fast write.

The game that is barely playable at times is oblivion. The framrate dips to single digets when fighting multiple characters. It is also very low in town, but in the dungeon and in houses it is fine. This happens regardless of what my video settings are.

Half life 2 has occasional stutters, but got really bad at the last level of the game (10-15 fps). Oddly FEAR is the game that performs the best. With near maximum settings in the demo I got over 40 fps with no noticible drops. This is the only game that performed similarly to benchmarks.

I assume that my processor is probably just too slow since it is a 2400+, but I don't know if the fast write or agp write options are having a large effect also.

I am thinking about overclocking my cpu, but I don't have any options to do so on my old ecs motherboard. I may just give up trying to play oblivion since it is the only game that is unplayable right now and I don't really wanna spend another couple hundred just to play the game especially since I would have to upgrade to an agp motherboard.

System
athlon xp 2400+
radeon x800xl
1gb ram @ pc 2100
ecsl7vmm2 motherboard w/ onboard sound and 4x agp