To allow two letter acronims and Camel case identifiers

Office Button > Excel Options > Proofing > AutoCorrect Options > AutoCorrect > Correct Two Initial Capitals = Yes->No

To open xlsx files in a separate window

http://myitkb.net/83/open-excel-2007-spreadsheets-in-different-windows.html�
Windows Explorer > Tools > Folder Options > File Types > xlsx > Advanced > Open > Edit > …
…Application used to perform action = "C:\Program Files\Microsoft Office\Office12\EXCEL.EXE" /e
…Use DDE = Yes -> No
…Application used to perform action = "C:\Program Files\Microsoft Office\Office12\EXCEL.EXE" /e "%1"

To open xls files in a separate window

http://myitkb.net/83/open-excel-2007-spreadsheets-in-different-windows.html�
Windows Explorer > Tools > Folder Options > File Types > xls > Advanced > Open > Edit > …
…Application used to perform action = "C:\Program Files\Microsoft Office\Office12\EXCEL.EXE" /e
…Use DDE = Yes -> No
…Application used to perform action = "C:\Program Files\Microsoft Office\Office12\EXCEL.EXE" /e "%1"