Instructions
Launch SRB2. Click "Options" followed by "Video Options" and "3D Card Options."
Change your "Gamma" settings so that your RGB (red, green, blue) values are all equal.
Go back to "Video Options" and select "Resolution." Lower your resolution. Test each time you lower to see how lag changes.
Set your textures to "Bilinear" in "Video Options" to lower the texture count in your OpenGL game. Your textures have lower quality, but your lag decreases.
Remove "Anisotropic Filtering" under "Video Options." The anisotropic filter enhances the quality of your game's textures, rendering smaller details and fixing blurry edges. However, rendering textures to this degree also creates lag for older computer systems.
Close all unnecessary programs and browser windows. Press "CTRL," "ALT" and "Delete" keys to bring up the system monitor menu. End all processes that are unnecessarily taking memory away from your "SRB2" game.