Here are some simple 2D games for Windows, made by me. The requirements for these games are really low, that means that they problably will run on a Pentium computer without big problems.

Puma Invaders - Screenshot

Puma Invaders

Game inspired int the classic "Space Invaders". Arrow keys to move and Control (Ctrl) key to shoot.

Stark Pac - Screenshot

Stark Pac

Another game inspired in the classic "Pac Man". Arrow keys to move the character.

PWG2002 - Screenshot

PWG 2002

3D game for programmers, where you need to code your character to kill the oponent.