I see your running LOW profile 512 mb for this moment in time.
Now let me give you and example of why this is happening.
I run two exact same make and model 19 inch Dell wide screen monitors on my computer.
Now one port is DVI and one is VGA.
Even with two exact same make and model screens the VGA one is always slightly darker then the DVI one.
I tried everything I could think of to alter this state.However after speaking to others and trying many diffrent things I came to the conclusion it was just the VGA port and power consumption.
I agree with RandyL your power supply is pants.This maybe part of your problem,hence I say could be an issue with power consumption.My issue is not power consumption as I have a 500 watt PSU.
ALL hardware degrades over time regaurdless of how well you look after your computer.
I see low ended GPU and a lower ended PSU is part of your issue.
Buy a GPU with twin DVI.
Buy at least a 500 watt PSU.
I have never known a low eneded GPU with a DVI port and a VGA port to give the exact same effect on both monitors.There is always a slight diffrence.I just over time didnt notice it anymore.However I would say there was always a diffrence on yours but it was so slight you never noticed it,now your computer has degraded over time the effect is more noticable.,
I also see you are using two diffrent monitors.Possible cause.
I use exact same make and model and still have issues.
Power consumption for the HP monitor is 60 watts on its own.What model number is your Teknika?
Add to that all other components that use power,your power supply needs an upgrade and time for a new GPU.
You are running a basic HP branded computer,it is a P4 with HT.Low budget computer.
Anyone else see what I am seeing?