To change the width of columns in Datasheet View:
Move your mouse to the right edge of the column that you want to resize. When the cursor changes to a double arrow, hold down the mouse and drag to the left to make the column smaller or to the right to make the column wider. Select the entire column by clicking when the cursor changes to a down arrow. Click the Format menu and select the Column Width... command. Click the Best Fit button to resize the column to fit your data.