Immediately after powering on (or resetting) system, press (and release) the F2 key over and over again until the main Visual BIOS scene is seen or 15 seconds has transpired. Do not wait for something to appear on screen before beginning to press the F2 key; begin immediately after powering on.
On some older BIOSs, Visual BIOS is unable to display if the monitor is not able capable of operating at the 1024x768 pixel resolution. Check the specifications for your monitor to see whether this is the issue. If this is a TV being used as a monitor, the likelihood of this being the case is higher. Again, check the specs...
Hope this helps,