Open Multiple Instances of Excel without PERSONAL.xlsb Lock Message

Unhide your Personal.xlsb and turn on the share workbook option. You can then open as many instances of Excel as you want without that pesky read-only message.

The only drawback is that if you want to actually add or edit a personal macro you will have to unhide Personal.xlsb again and turn the share option off again (you can't see or edit macros of shared workbooks, but you can run them.)

To find the share workbook option, press the 'Review' tab and then press the 'Share Workbook' button, which is in the 'Changes' group.

In Office 2007/2010, unhide personal.xlsb by opening a single instance of excel and choosing unhide from the view tab, window section, unhide button In Office 2007, share the workbook from the review tab, changes section, share workbook

If you are not reliant on your personal macros, you can navigate to:

C:\Users\user name\AppData\Local\Microsoft\Excel\XLStart

and make the Personal.xlsb file read only. That should stop the nagging.

If 2 instances aren't necessary, you can also force Excel to open a new window for each file. It will show multiple instances in the taskbar (which I assume you can drag across monitors) but it will only have 1 copy of Excel running.

This thread provides some options on how to stop this from happening. I have not had a change to test Excel 2010 multi monitor support but I can confirm that 2007 has no way of supporting one instance with files open on multiple monitors.