If you don't have a top-of-the-line rig, playing first-person shooters and RPGs on your PC doesn't always work out. Strategy and simulation games tend to be gentler on your system, though, as the recommended system requirements for Tropico 3 prove (via Blue's News):

• Intel CPU - Core 2 Duo E6400 2.13GHz
• Nvidia Graphics Card - Geforce 7600 GT 256MB
• Direct X - 9
• Ram - 1 GB
• AMD CPU - Athlon 64 X2 Dual Core 4800+
• ATI & Intel Graphics Card - Radeon X1600 Series
• Hard Disk Space - 5 GB

Tropico 3 is currently in beta. It'll be released in September.