Right click on the picture and select “Save as picture”. Chose somewhere where you will find it (!) and save as jpeg (this is such a universal format I would imagine all websites would handle it).
Find your picture and upload to the website.
I got this from trying with PowerPoint 2007, but I think the method is identical for Word 2007. If not, click and drag the picture into PP first and do as before (I’m in Word 2003 and don’t want to switch over right now to test).