Computer Laggy after connecting second monitor ?

[ZufaelligeFenster]

I wasn't quite sure where to place this since I'm not really sure whats wrong. A couple of months ago I bought a larger monitor to replace the one I had as my primary monitor and set my first monitor as my secondary. So I have a dual monitor setup. The first few weeks or so everything was fine but I started to notice that my programmes were laggy. I am a character artist and I noticed a lag in Photoshop and Zbrush when I move the pen across my wacom. I uninstalled and reinstalled all my wacom drivers so I knew they weren't it. Then I started noticing that my CPU would spike a lot if I had say Photoshop open on my primary monitor, and firefox open on my secondary looking for references. Firefox would load really slowly too - I am on wifi and as far from the router as can be but it seemed slower than it used to be, and I would get "(Not responding)" a lot. I didn't think much of it until my computer just completely stuck itself down once while I was working. I luckily had just saved my work, but it all seems related to adding this second monitor. This week it shut itself down and when I powered it back on it wouldn't boot so I hard reset it and it went to reboot repair which really terrified me. I'd be out of business for a long time if I lost my computer.

Anyroad, after that I unplugged the second monitor to see if it really was the problem and so far there is some lag but not nearly like it was. I don't get that super annoying pen lag in Photoshop, but now I don't have enough desktop screen for my work and my references so I have to import them directly into Photoshop, which causes enough of a lag to be annoying. I'm almost wondering if my system is just too old to be running two monitors, or many of these programmes. Its a custom build, but its going on six years now and the only thing I've done had been upgraded from 4gb RAM to 8gb. I've wondered if perhaps it is my graphics card, even though it is capable of supposing dual monitors, maybe its too worn down from 6 years of Photoshop and Zbrush and other visually intensive programmes and games. Maybe its my motherboard, its old and dusty and doesn't run as fast as it used to, and just can't keep up with these programmes. I've noticed too Photoshop takes a minimum of 20 seconds to open and crashes more often now which made me wonder about the motherboard (I'm not super tech savvy, but I try to at least understand the basics). But many its just not enough RAM to allocate everything I'm trying to do at once.

I'm really looking for solutions, anything that might help me use the two monitors. If the consensus is that my hardware is just too old and needs replacing, any suggestions for what needs to be replaced right away would be great.

What I have tried:
Turning off transparency
Changing to windows basic
Lowering resolution on games
Turning off all but necessary start up items (mouse, keyboard, etc)
cleared caches for programmes like After Effects and Maya, etc
exit programmes fully when not in use
stopped background programmes other than antivirus (Avast)
checked for Windows updates
checked for graphics card updates
checked for Wacom updates

Here are my computer specs
Windows 7 home Premium 64
Intel Core i5-2500 Processor (4x 3.30GHz/6MB L3 Cache)
Liquid CPU cooling system (SOCKET-1155 and 1156) Standard 120mm Fan
2 x 4GB HyperX RAM (8GB total)
Nvidia GeForce GTX 570
Gigabyte ga-h67ma-usb3-b3 motherboard
750 Watt Corsair CMPSU-750TXV2
500GB Hard drive
Both monitors are LG

let me know if you need to know anything else about the system. Please be as thorough with any instructions as you can, as I don't know a lot about how to work on computers and thank you for any help you can provide.

 

[Technologify]

What is the monitor resolution? You can try to lower the resolution of display.

 

[CBender]

Generally older nvidia cards are pretty bad when it comes to multiple monitors configs. The thing is that when adding a monitor the gpu treats the entire desktop as a 3d (D3D) application instead of a 2d (single monitor). You should also see a rise in temps and fan activity under idle load.

Unfortunately i don't think that there is a solution to this.

 

[ZufaelligeFenster]

Most of the 3D programmes are not compatible with lower resolutions so that unfortunately would not work. I have many of them on my laptop and the UI is just awful at the interface it has. A lot of what I do is size and resolution dependent. Photoshop I could probably get away with a lower resolution but then I'd just have to switch it back and forth on a daily basis.

I was pretty convinced myself that I'd just need to start replacing things. Any suggestions as to what I should replace right now and what can wait til later?

EDIT: My computer just overheated by the sound of it while I was playing a game and the screen shut off though I could stil hear the game. Had to force shutdown, the second monitor was still unplaugged at the time so yeah, time to replace things.

 

[CBender]

I would start with the gpu and an ssd (couldn't tell). The best gpu for this kind of workload (for me at least) would be a 1070 by nvidia. Of course if you come with a budget we would be able to help to a better extent.