Are you using nVidia's latest drivers? Also please don't set everything to High.
Turn rendering down to Medium.
I think I've already tried that, but I'll try again in a few minutes and let you know how that went.
I have a high-end gaming PC, and the game runs terribly on that too. No matter what settings you choose, the game will run poorly.
Basically, Rockstar screwed up with this port. All you can do is turn the settings right down and hope that they eventually release a patch to improve performance.
Are you aware of any such plans in the nearby future?
Nope.
Rockstar is basically refusing to acknowledge that there is anything wrong, despite the massive uproar in the PC gaming community when the game was released.
Rockstar's official line is that only one percent of users have called the phone hotline, so 99% must have no problems. They have also advised users to run everything on low settings, because "higher settings are provided for future generations of PCs with higher specifications than are currently widely available"... which is nonsense, because there is nothing particularly spectacular about the higher detail levels when compared to other games, and the performance barely seems to improve on ultra-high-end PCs.
I'm still hopeful that there will be a proper patch eventually, but it will undoubtedly take a fair bit of work, and will be reliant on Rockstar deciding that it's worth the effort.
Here's Kotaku's article on the debacle, with links to some related forums:
http://kotaku.com/5101687/grand-theft-auto-iv-on-pc-is-a-little-broken
Bummer.
I can't say those were 45 well spent.
Yeah, you're not alone. It's been one of the biggest debacles in PC gaming that I can remember.
Still, the game is quite playable on most PCs at low detail levels, so it's not like the disc is a coaster. It's just a bit disappointing that Rockstar dropped the ball.
The people who I really feel sorry for are the ones who decided to upgrade their PCs when they saw the poor performance, only to find that it didn't make any difference at all.