i have Archlord, it's actually a nice mmorpg, at least, now since it went free. Despite my oh so negative comments in the past

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Would cost you 30 USD, which isn't much.
my friend has a standaard pc (3.0ghz, 512 ram and a low end ATI) and runs it just fine.
About shooters, i already forgot about BF1942 (have that too), and i agree with whoever said it, use the modern combat mod, it's a real trait.
Ut2k4 is also a nice shooter. But if you like more involving shooters, get half Life 2 GOTY (with HLDM and CSS). That's one of the most amusing games around in multiplayer, toilet throwing ftw.
But euh, it would be easier if you could post your specs here, if you did already, i overlooked

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Would be easier to pointing you out to a potentially good game