PDF-XChange Viewer the default PDF Viewer

- click Start -> Run, then type "cmd" and press Enter

- Right click the cmd.exe result that is shown and select "Run as Administrator"

- cd "C:\Program Files\Tracker Software\PDF Viewer" including the quotation marks, then press Enter.

- run this command: PDFXCview.exe /makeassoc:web=true and press Enter again.

thanks