Klumpen0815: WinXP 32bit with Athlon II (3 cores) here, runs
very badly (slide show) especcially when controlling a police car. :/
System is very clean, Gothic 3 and Race Driver Grid run extremely well.
Any tips? :/
Edit: Got the SimCity4 launcher and performance has gotten a bit better via multicore correction and window mode in software rendering but still not really good.
The GOG shortcuts already set the single core option, and they have a windowed shortcut too, so those two aspects should already be taken into account.
My recommendation is to use hardware mode and once you've launched the game go to the options and turn the shadows to the low option.