Oh - I am very sorry to have "mistagged" you. I was kind of aware, that July is a name that is mostly feminin, but I still fell back to talking about the (unspecified) user (which is maskulin in my language..) ... but I guess you don't take it as a serious offense

The minimum requirements on RAM to run Windows isn't 512, it's 128.
Well, we were not talking about running Windows. We ware talking about running Windows AND Planeshift.. at the same time :-P
Anyways, 128 IS the official minimum requirement for WinXP, but you will have trouble already once you start opening a browser or an office suite. Still somewhat usable, but the system has difficulities to react. I would recommend 256 MB to make good use of XP, but this doesn't really matter, because Win98 and others are NOT an option (security and stability issues) and many people wouldn't like switching to a Linux without KDE and Gnome (colored stuff to click on)..
Back to Topic:
This night (the sun starts going up in my part of the world right now) I installed Planeshift also on my Windows XP partition.
First I tried running PS with the standard Graphics driver that came with my windows installation (a version from 2004..). It took a while to get to the login screen and then it was so slow, that I didn't manage to type in my email address.. not a single letter. Is the login screen even 3D?
After installing the new driver from nvidia.com I tried to run the game again:
It was running good with the standard settings (apart from the fact, that I needed it to run as Adminstrator) and I could even set it to 1280x1024 (my native screen resolution) fullscreen. Standard Settings is: 1024x768, 32 bit, with sound, vertext to off, no loading of maps checked but the preload models box checked.
I did get a runtime error when I tried the game without preloading models, but this isn't an issue, since it runs fine while preloading models.
I had AVG (Anti Virus) running, but nothing else.
So I have PS running in both Linux and Windows (not at the same time though

) with 512 MB of RAM, 800 MHz CPU (that is 100% used nearly the whole time) and a GeForce 5200 PCI with 256 MB. And today at the fortress (I was using the fixed zip, because of the blackness issue) everything was reaaaally smooth.
Before I forget it: Ingame I was using Adaptive Distance. I did set it to 25 minimum, 15 fps minimum and 25 fps maximum. My framecap was around 55, but I don't know if this value even gets used when I set Adaptive Distance, unless I can see from one side of the map to the other..
Maybe this information helps somehow. I can also check other stuff if asked to. What is important to me: You CAN run PS on Windows and Linux with 512 MB of RAM and a 800 MHz CPU. There is NO point in saying: "No chance, get a better PC".
PS:
Getting 1 GB of RAM could still be good to speed up the system, but is not completely necessary, like I said.
*searching for "he" in his test*
..
*is reliefed to find 0 occurencies of "he"*
