I'm sure this has been discussed a million times over, and I've checked as many topics as possible to find a suitable solution to my problem, but alas...

So I see no other option than post a new topic and pray that someone can hand me a solution I haven't already tried.

Intel Core2Duo 6400 @ 2.13 Ghz
Geforce 7900 GS (256 MB)
2 GB RAM

I have a European PC DVD-ROM version of BGE
(patch-applied version)

The game runs excellent with all settings maxed out. With the exception of one: Water. Unless the water is set to lowest-detail, slowdown is inevitable when near 'open water'. I can't even run the game in 1024 with AA, glare and shadows off and moderate water FX on in '1024' res without experiencing some serious slowdown. I've downloaded the latest drivers for my video card, applied a Windows hotfix for multi-core processors, and I can't seem to lower my video memory, in the bios or with PCI latency Tool (I can only seem to select PCI or PEG), otherwise I would've tried that, too.

If anyone has any other ideas, they would be greatly appreciated. I love the game, and since Hyllis is very much a water planet, I would love to make use of the water effects, since they really make a difference to the graphics, and logically speaking, my pc should be able to run the game with ALL settings maxed out. Sadly, as I've seen from the rest of the topics, the PC port of BGE wasn't exactly top notch.

Thanks in advance

This sounds like the same problem people had with the Geforce 6600GT. I never found a way to solve the problem except for using old drivers but of course those aren't compatible with the newer video cards anymore. While the PC port has a lot of problems, this problem only appeared after Nvidia updated their drivers. Try diabling Triple Buffering in the compatibility settings, but if that doesn't help I'm afraid you're probably going to have to play the game with the water on lowest detail.