Help me with this monitors ?!

Hi all ,
I got an ATI Radeon HD5570 for my Dell Pentium 4 desktop whose OS is Windows 7. I also got two monitors along with it. They are both working good when I plugged and tried them, except when I tried the full screen mode while playing games or watching movies. I can view it in the main monitor, however, the second monitor does not work whenever I switch it to full screen mode. Is it not possible for me to run a game or a movie in full screen mode while running another program with the second monitor? If not, can I split the screen or convert the two monitors as duplicates? Cause I think I might be missing something. Thanks in advance!
