Tools>Options>Calculation can be Auto or Manual.

Excel takes the Calculation mode each session from the settings on the first
workbook opened in that session.

i.e.  If you saved Book1 with calc mode in manual and opened it first, calc
mode would be in Manual.

If you saved Book2 with calc mode in auto and opened it after Book1, Book2
would be in manual mode(Excel ignores the auto calc mode in this case).

If you close Book1 before opening Book2, Book2 will be in auto calc mode.

Confusing enough? <g>

It may be safest to place some Workbook_Open code in your Personal.xls which
sets the calc mode.

Private Sub Workbook_Open()
Application.Calculation = xlCalculationManual
End Sub

Or in a particular workbook you want in manual mode.

Gord Dibben  MS Excel MVP

Gord Dibben  MS Excel MVP