In order for you to play Castle Crashers on Windows with minimal graphics settings, your computer must meet the following requirements
OS *:
Microsoft® Windows® XP / Vista / 7 /
Processor (CPU):
Intel Core 2 Duo 2GHz+ or better
Memory (RAM):
1 GB RAM
Graphics Card:
256 MB video card
DirectX®:
9.0c
Hard Drive:
255 MB HD space
Sound:
DirectX compatible
Other Requirements:
Broadband Internet connection
Additional:
Supports Microsoft® Xbox 360 controller or Direct Input compatible controller
Additional:
Ultra Graphics Mode requires a 64-bit OS, at least 4GB of RAM, and a 2GB VRAM.