You need to create a new default template that will load at startup. They didn't make it easy to do in Office 2007! But here's how:
- Open a new blank worksheet.
- Insert > Hyperlink > Paste in any link
- Home > Styles > Right click on the 'Hyperlink style' > Modify > Set your font options
- You probably will want to do the same for the 'Followed Hyperlink' style
- Delete the hyperlink.
- File > Save As > Other formats
- Browse to "%APPDATA%\Microsoft\Excel\XLSTART" (Copy/Paste that into the File name field and press Enter to get there easily)
- Save as type: Excel Template (.xltx)
- File name: Book.xltx
Now whenever you start Excel or create a new workbook, the hyperlink font should be the one you choose.
This Microsoft support article helped me: http://support.microsoft.com/kb/822107 look here for where to save templates for Office 2003, or to see other ways of loading your template.