To anyone who's interested, any type of image can be transparent, be it Bitmap, PNG, JPG or GIF, the secret is "Chroma-Key" If there's a white background on the image(or any colour, for that matter), drop your image onto a PiP(overlay) track, click on "modify", a PiP designer window will appear, adjust the size of your image(as and if required(a grid of up to ten "squares" is available, plus TV safe zone. Options will appear in "Properties" including Chroma-Key, click on Chroma-Key, a little arrow to the left of where you "tick" will, when clicked, point down to reveal settings. Click on the eye dropper(pippet) and, in the image area, click on the colour of the background you want to "vanish", and thus it will, leaving only the arrow, pointer or any other icon you want superimposed on your video. All quite easy, really!
Cheers!
Neil.