The directories below are the default locations for where the presets are saved -- if you have moved the preset to a custom location, go there and then follow the instructions below.

To delete a preset:

• On Windows Vista and 7, go to: C:\ProgramData\GenArts\Sapphire\presets\GenArts
• On Mac, go to: /Library/Application Support/GenArts/Sapphire/presets/genarts/

​Select the preset you want to delete. (They are in this format: S_PluginName_PresetName.gp.)

Right click on the preset file and select "Delete".