From what you're saying, I gather that your problem is simply laggy games.
Could you provide the following information:
- CPU
- GPU
- RAM
If you don't know where to find them, follow these intructions (since you mentioned Pentium, I'll assume you're on Windows XP):
1. Start > Right click on My Computer > Properties > General Tab > Computer (here you'll find your CPU and RAM)
2. In the same window, Hardware Tab > Device Manager > Display adapters (here you'll find your GPU)