How do I determine the version of Xfree86 that is in use ?

Hi everyone

It is no doubt probably obvious to those who know but could someone please tell me how I can easily determine the version of XFree86 that I am using ? (This is because I wish to install the gatos ati all in wonder driver and it warns about mis-matching versions).
It would be great if I could easily determine the version number via somewhere in the KDE interface.

Thanks in advance

WindozeEscapee

(I am using a hard disk installed version of knoppix 5.1.1 I believe)