There are 2 ways to find the firmware version of your Canon Powershot SX10 IS camera. Easy way is using the freeware tool called CameraVersion. Using it is pretty easy. open CameraVersion and select a jpeg image which was taken from your camera. it wills show you the firmware version and many more details. Remember you have to use a jpeg image before editing it in any software like photoshop.
Second method of finding the firmware version of your camera is create a file and name it as ver.req then move it to your SDHC card using a card reader. Now press the replay button and then click FUNC Set + DISP buttons same time. camera will display the firmware version.