I am having slowdown problems on Windows 8. Is there anyway to fix this? I have tried compatibility mode, but that does not seem to work. I tried to HI-Res patch but that slows the game down even more. I have however patched the game up the the latest unofficial patch from 2009. That helped a little bit but I am still experiencing frustrating lag.

Any help?

there is already a thread that talks of possible solutions but none have worked for me. i really like to revisit Arcanum every now and then and maybe the best thing to do is rollback to Windows 7, if no solution can be found.

Or use Linux. The windows translation layer Wine will always work, and if it doesn't you can use a previous version through a prefix manager like playonlinux for a specific program.
Also it's free.
That said. Try using wined3d.dll on windows, as I imagine it's a rendering issue, and this might fix it.
http://www.nongnu.org/wined3d/
Just put the dll in the arcanum directory where the exe is.

so i went ahead and downloaded the Arcanum installer (version 2.0) from GOG and now it seems to be running alot smoother now.

EDIT: forgot to mention that i added the -doublebuffer parameter to the shortcut.

I'm not sure what it was that fixed it for me but this is what I did.

1. Installed the latest version from GOG
2. Installed some patches (fan patch, townmaps and resolution)
3. Deleted ddraw.dll
4. Added " -window" to the Shortcut (right-click properties then edit the target)

This may not work for everyone I dunno.

it should run in full screen as windowed mode is no fun. anyways, i did uninstall Windows 8 and went with Windows 7 HP. Arcanum now runs the way it should, i.e. no lag at all.

Just another reason to hold off upgrading to Windows 8 for as long as I possibly can. No upside (unless you have a touchscreen, which I don't) and way too many downsides.