In my desktop computer, when i turn on my computer,it shows the msg"Not optimum mode,recommended mode 1280*1024 60Hz?"

what's the matter w/ it?
is it the hardware or software problem?I dunno about it.

The computer is booted until the window..becoz my fd told me I could be online but the monitor cannot work
Could anyone solve it w/ some suggestion?I m in urgent...
thank you!!