have you upgraded anything since you purchased it

when it starts do you see the post screens and when it hands over to windows you lose the monitor
if that is what is happening, see what happens in safe mode,if it boots fully into windows contact dell as your psu may be faulty

 

I Have Not Upgraded. I Am Quite New At This. Yes, It Shows The Dell Screen And Goes Right To Power Save Mode. Green Lights For A Few Seconds And Then To Yellow On Tower And Monitor.

 

tap f8 when booting and from the options screen try safe mode
i have asked someone else to look at the problem also as i don't know much about dells

 

What model is this Dell?

 

Dimension C521