Running Pcsx2 Games on 512 MB RAM

Maybe. You didn't specify what video card you have
It needs to support Pixel Shader 2.0.

PCSX2 FAQ @ Next Gen EMU forums
Minimal Specs:
AMD 64 or Intel Pentium 4 (VM Build will not work with non SSE2 CPU's)
512MB of RAM
Pixel Shader 2.0 supporting video card

Recommended Specs: (For reasonable performance in many games, but not all)
AMD64 X2 or Intel Conroe E6600+ (Multi Threading is supported in PCSX2)
512-1024MB of RAM (more RAM allows for VM mode to be stable)
Pixel Shader 2.0 supporting card (recommended GeForce 6600-8800 or equivalent ATi card)