Excel 2007 : Excel to webpage image issues

When trying to save an excel workbook as a webpage the chart images created in the webpage files are being produced in duplicate (one gif and one png file for each chart image). I had Firweorks installed and figured that may be the cause so I uninstalled it. I also have the 'Allow PNG' unchecked in the Web Options.

I previously had no problem when I was using Excel 2003 and I have now tried again in work in using Excel 2000. On both cases only gif images were created - which is what I need.

So, PNG files appear to be created by default. I figured it must be a setting within Excel 2007 somewhere.

Can anybody help me resolve this.

After further investigation it appears that a set of PNG images is created when the 'Allow PNG' is on. When unchecked I get the GIF files. However, for both cases I get a further set of PNG duplicate images which appear. So irrespective of the 'Allow PNG' setting I always get a set of PNG images.

Does anyone have any idea why?