Glanerch :
in Excel [Version 12] hypers did open .jpg files with Photo Viewer now they open with IE [version 8] - why ?
Excel ignores the file association between the .jpg file extension and your preferred application for viewing images and always defaults to Internet Explorer.
I finally found a registry fix for this problem.
The original solution was posted by Daniel Stawicki in his (Polish) blog entry “Hyperlinki do plików jpg w Excel 2010/2007 otwieraja sie w IE8”. For those who don`t read Polish (me included!), Google Translate will provide enough information for you to figure out how to apply the patch. However, since the translated text (particularly the value data to be changed) is a little garbled, the following step-by-step instructions may assist:
(1) Run regedit.exe
(2) Navigate to HKEY_CLASSES_ROOT -> jpegfile -> CLSID
(3) Right-click on “Default” (the Value Name) and select “Modify”
(4) Change “Value data” from {25336920-03F9-11cf-8FD0-00AA00686F13} to {FFE2A43C-56B9-4bf5-9A79-CC6D4285608A}
This registry patch is said to fix the problem for both Excel 2007 and Excel 2010 running in Windows 7. It certainly works for Excel 2010. I haven`t tried it with Excel 2007.