If you are first opening Excel and then opening the desired workbook,
creating Book1.xls is normal.  If you're opening the workbook by using
Windows Explorer and finding the .xls file and double-clicking to open it
directly, then it's not.  You may have a Book1.xls in your XLStart folder.

But to start Excel without the splash screen and without automatically
creating an empty Book1.xls follow the instructions under the Excel Help topic
Customize how Excel starts
and look in the sub-topic
Use startup switches when you start Excel
which will tell you how to do it all, which boils down to using the /e
switch in the shortcut opening Excel to prevent display of the startup screen
and a new blank workbook.