I've recently re-installed Arcanum, the installation process went smoothly. I have also applied the fan-made patches: Unofficial Patch, High Quality Town Maps, High Resolution Mod. After doing those, I ran the game to check if everything was running smoothly.

The first thing I noticed was that the mouse movements lag slightly, a minor annoyance. In fact, the entire game was lagging a little. I quitted and noted that the computer was running slower than usual. So I checked the task manager and saw that the CPU Usage was skyrocketing around 70 to 90%.

Restarted the computer and added the commands, -no3d and -doublebuffer. Didn't help much and perhaps made the game lag more. Quit the game, same issue. Tried windowed mode and also removed the commands mentioned above and quit the game again. Strange enough the CPU usage was normal. However, the mouse lag was still present even if I ran the game in windowed mode.

I'm not exactly sure what to do now, games such as Fallout aren't giving such problems. Only Arcanum for some reason. I could really use some help to get this game working perfectly. I'll provide my computer specs below...

Windows 7 Home Premium 64-bit SP1
AMD Athlon II X2 250e Processor
4.0GB RAM
ATI Radeon HD 4270

Almost forgot, I've set the Arcanum's shortcut to run as an administrator.

I think the first thing you need to do is see if you have the same issues with just the basic download package, without all those mods. If you don't, those mods or at least one of them is the issue. If you still have issues, then we can look at your settings and hardware. How big were these modifications anyway?