These are the official Shadowgrounds system requirements.

MINIMUM SYSTEM REQUIREMENTS
Operating System:	Windows XP/2000
CPU	1.3-1.5 GHz
RAM:	384 MB
GPU:	GeForce 4 Ti 4200 or ATi Radeon 9000 or better
	1 GB free hard drive space

RECOMMENDED SYSTEM
Operating System:	Windows XP/2000
CPU	2.0 GHz
RAM:	512 MB
GPU:	GeForce FX 5900 Ultra or ATi Radeon 9500 Pro or better
	1 GB free hard drive space
	Joypad for co-op play