You can change it, but I bet you won't want to.

You can change the normal style of a workbook by:
format|style|choose normal from the dropdown
click on the modify button and change the format to what you want.

First bad thing:
Styles are kept with workbooks. So you'll have to do this to any new or
existing workbook.

Partial good thing:
You can create a workbook template named book.xlt and store it in your XLStart
folder. If you change the normal style for this template file, then any new
workbook that you start by clicking the New icon on the standard toolbar will
inherit this style.

Second bad thing (and why I bet you won't do it):
Dates are numbers. If you change the normal style to (say) two decimal, then
type a date, you'll see the trouble. (Interesting, (well, to me anyway), typing
a time doesn't cause the same trouble.)

Andrew wrote:

Is it possible to change the default number format in Excel?

--

Dave Peterson