A few months ago I first upgraded my PC for gaming. This is the first time I've had a gaming PC in over 12 years. Now I have to admit, I enjoyed the simplicity of my Xbox 360 and PS2, but it's nice to  be able to mess around with components, customizing things and all that. I feel like I'm learning a lot, and loving it. At the same time, however, I've had a lot of headaches. My PC won't start up all the time, and I'm finally going to send my power supply back this weekend to have it replaced.  Also, now my monitor has been freaking out and not getting a signal. It's my computer or video card or something - I think it might be the drivers. Overall, though, it's good to be back in the world of the PC.

A few months ago I first upgraded my PC for gaming. This is the first time I've had a gaming PC in over 12 years. Now I have to admit, I enjoyed the simplicity of my Xbox 360 and PS2, but it's nice to  be able to mess around with components, customizing things and all that. I feel like I'm learning a lot, and loving it. At the same time, however, I've had a lot of headaches. My PC won't start up all the time, and I'm finally going to send my power supply back this weekend to have it replaced.  Also, now my monitor has been freaking out and not getting a signal. It's my computer or video card or something - I think it might be the drivers. Overall, though, it's good to be back in the world of the PC.

It sounds like the power watt supply isn't giving you enough juice. Also if your not getting a signal, it's obviously from the videocard. Still you should get a picture from using the gpu's dvi slot or whatever your using.  
 
Maybe giving us more info to work with will help, like what videocard, what psu, cpu, ect.

Now you can play Age of Empires III!

'Upgraded your PC for gaming' - elaborate please.  You upgraded a non-gaming PC?  Or built it from scratch?
 
I agree with Hitman, your PSU not being powerful enough is the most likely candidate.  As in, you need to get a better one, not just replace it like for like.