Posted: 2006-03-31 01:01pm
I think your problem is the RAM. My system is almost identical otherwise, and it runs beautifully with large textures, 800 x 600, and all other settings at default.
If you're talking to me, then I think you're right. The game seems to have a memory leak somewhere and it thrashed that system pretty bad after it had been running a few hours. More RAM alleviates that problem quite a bit. My brother's using that PC now with an extra half-gig of RAM salvaged from his old, busted rig and it runs pretty smooth from what he's told me about the last few hours he's been playing it.
Also, not sure that a 128MB card is enough for large texture size, but that's just speculation on my part. It's not like there's a tab in task manager for used GFX card memory.
Right now, I'm on an Athlon64 3200+ with a gig of ram and a 256MB x800GT and performance really isn't an issue with the automatically selected high graphics settings. I played the game for an hour or so and it performs pretty damned well for the looks. For a Bethesda game, it's a masterpiece of programming work.