computer peripherals

I have a mitsubishi Diamondpoint SB70 that my mother gave me because my HP monitor just quit turning on. The first time I plugged it in it turned on and all of the Icons were big and pixely. I went to adjust the screen resolution and the screen went blank and then there was a red and whit box that I cannot get rid of or do anything with. It says : Attention Signal Frequency is out of range FH>86.2 FV>59.9 Please change signal timing.

I cant do anything, it wont respond to anything I do. Ive turned off the computer unplugged the monitor etc, etc. What do I do?!!!!!!!!!!!!!!!!!!!!!!!!