Why does my CPU Usage reach 100% too often?

I'm using a dual-core processor and often see my CPU usage reaches 100%. I realize this may happen if I'm running too much applications, so when I know the computer starts to run slowly, I start to close my applications.

I usually run 4-5 applications simultaneously. Usually those are: web browser (Google Chrome), Adobe Photoshop, Notepad++, XAMPP, and Windows Task Manager. Usually I close tabs in my Chrome first, because I often browse the net with about 20 tabs/4 windows open, so I presume that would take much memory (bad habit, I know).

But even after closing Chrome's tabs or closing other applications, my CPU Usage often stays at high percentage - 72% at best, 100% at worst. I check the Processes tab on Windows Task Manager and usually found the System, System Idle Process, or services.exe taking the highest CPU process (could reach 60).

Why is this happening? And is there any solution?

EDIT
I have T2250 @ 1,73 Ghz and 2.5 GB RAM

System

If this process is causing high CPU usage, it's a driver. See these questions for further analysis support:

• How do I get to the root cause of high Deferred Procedure Calls?
• How do I troubleshoot a Windows freeze or slowness?
• What is the proper way of debugging a slow Windows installation?

System Idle Process

This process will use all remaining CPU resources that were not used by any other process. That's actually how CPU load is measured in the first place.

If the CPU spends 20% of it's time processing the Idle Process, then it's under 80% load. This process is nothing to worry about.

services.exe

services.exe is the service control manager and shouldn't really be causing you any trouble.

What could cause trouble is svchost.exe which is the host process for Windows services. Every service in Windows is started through an instances of svchost.exe. So if a svchost.exe is causing high CPU load, it's a service running wild.

You can use Process Explorer to determine which services run inside a service host by simply hovering over the process:

Image source

To be honest, based upon the spec of your computer I don't actually see any problem; Photoshop is a very powerful program and can take a massive amount of resources (depending on what you're doing with it of course depends on how much/little resource it will require). The fact the CPU distribution is dancing between programs is normal, all PC's do it. The fact that the CPU is so high is because you're maxing it out I would guess. Just because you close a program doesn't guarantee the RAM is released immediately. Coupled with it appears like you're pretty much running a dev environment I actually think your CPU is doing pretty well :)

As to a solution, quite simply do less or upgrade your machine!