Hello guys heres my story , i appreciate if you could reply and help me

I use to play wow heavily and really ejoyed it , towards the end of the wotlk days i got fed up and decided to stop playing wow , my game play all ran smoothly and all was well , Recently i decided to return to world of warcraft and thaught im gunna re set my pc to factory settings to clear all my old rubbish from days gone by e.g music videos full of junk.. after doing so i installed all the wows again apart from cataclysm and decided to jump on to see what the graphics were like , after coming on i experienced horrific lag , which i thaught strange since i never had it much playing before cata release days , i then decided to check out my interface options , I looked and all of a sudden the graphics bar , low fair high etc.. was all red , indicating i could not make it higher , which i thaught strange becuase i always use to be able to do it even tho i played low any way , So after then found a button caled reccomended graphics , I clicked this then all of a sudden my monitor turned of and flashed a message saying " input signal out of range " , i expericned this before but running wow repair tool always set it back to default settings , after trying to run it today its only doing files and taking 20 seconds and saying there is no bug , so i can not play wow for every time open the screen my monior goes to stand by saying signal input out of range , please help and kindest regards.