I am not familiar with Vector Linux but what you most probably need is the ATI binary driver from the ATI web page. Go there, download the driver *.rpm suitable for your ATI card and install in the following way:
1) switch to console mode via strg-alt-F1 and switch to runlevel 3 via "init 3" or - if this is too complicated for you - reboot with boot parameter "3"
2) go to the directory where you did save your ATI driver rpm-file
3) type "rpm -i rpm-file
4) follow the instructions
5) if that is finished, type "aticonfig --initial"
6) at that stage in opensuse you call a tool called sax2 which lets you set the settings for your graphics card etc. but I don't know how to do it in Vector Linux.
Perhaps there is some help given in the README file of the ATI rpm file