By default all cells in a worksheet are locked when sheet protection is
enabled.
It is up to you to decide which are to be locked or unlocked when the sheet
is protected.
Format>Cells>Protection is where you would change the "locked" or "unlocked"
status.
Select all cells and unlock them.
Select the cells to be locked and lock them
Then Tools>Protect>Protect Sheet.
Note the selectable options under "allow users to" when protecting.
Gord Dibben MS Excel MVP