With Windows™ XP, new icons with partial transparency were introduced: 32-bit icon images with an additional alpha channel (RGBA) or alpha-blended icons.

GConvert completely handles the handy 32-bit icon format for Windows XP with full alpha blending (i.e. partial transparency). GConvert draws XP icons correctly, saves them as they would appear under XP and can also keep the alpha channel when converting icons to PNG, PSD files & 32-bit BMP files – or converting these image formats to icons.

GConvert also can properly remove the alpha channel when converting an icon to an image format that doesn’t support partial transparency.

Finally you can also see the alpha channel of any icon thanks to the Alpha tab of the icon editor: