Alensot you are right i am using it because i am working on different types of graphics, e-book and other types of web applications that,s why i need CS3 rather i need the latest version of it, and to learn photoshop completely one need 1 to 2 yrs minimum for getting mastery in it, i have not taken any special course on it but i always play with it and always experiment on each and every controls so i get a basic idea over it.
Thanks.

One should have that interest within him to create new things while working in softwares like photoshop to get more expertise in that