Michel,
It's possible they have the machine desktop theme set to "Windows Classic" rather than "Windows XP", if that's the case they like squared off windows and controls rather than rounded ones.
>One of my client as a PC which has Windows XP SP3. This is the same OS as I have. He also uses the same browser as I have. We have IE 8. On his PC, the browser displays the control in the old style, such as with the old Windows 2000. Anyone would know is there is a theme setting somewhere that causes this?