Excel 2003 appears unable to sort the word Sun correctly.

Source data:

Column a Column b
An 1
Bc 2
Df 3
Ec 4
S 5
Su 6
Sun 7
Sunn 8
Sunny 9
Sun Microsystems 10

Sorted output of Pivot table with sort ascenging on Column A selected

Sum of b
a Total
Sun 7
An 1
Bc 2
Df 3
Ec 4
S 5
Su 6
Sun Microsystems 10
Sunn 8
Sunny 9
Grand Total 55

Any suggestions welcome...