How do I remove .PNG files from my "Documents" search?

Hi

How do I stop .PNG files from appearing in my Documents search results?

Details:
I think it is because I have got Adobe software installed (Photoshop & Dreamweaver), that the name that appears for the .PNG type of files in my Windows Explorer (Windows 7 x64) is "Fireworks.Doc, .PNG", rather than just ".PNG".
And the problem is that because it contains ".Doc" in the file type, I am getting all my .PNG files appearing in my search results. Obviously I only want hits for real documents e.g. .DOC and .DOCX and .TXT etc.

- Any thoughts?

John

---