I've tried to render the scenes in Blender for better light results, but I'm still not a friend with the program (it means I still don't know how to do it.. [O:)] ) so I had to add some light effects with Ps.

Blender does have a very steep learning curve. I'm waiting for the final version of 3.5 (3.6, or whatever version the final is) before I really start spending time with it.

Now I'm experimenting with some render plugins (Advanced, Uber, Phong) and with extra lights, but my computer don't like it.. [:))]

If it is helpful, you don't need to spend time trying all those different plug-ins. [:)] The uber and phong plug-ins you mention were just a test versions. We now have a final release version AdvancedRendering-1.6.sh3p or for users with lower resolution displays, there is AdvancedRenderingMini-1.6.sh3p (A smaller interface version of the first plugin)

As you may have read, phong was dropped because it had lots of limitations, plus uber can do everything phong can do and more! The plug-ins I linked to supperceeds all other rendering plug-ins, because they contain both shiny, and uber shaders.

Glossy setting = shiny shader.
Silk setting = uber shader.

For most renders the Glossy setting will be enough and is also faster.
If your scene contains any diffused surfaces or metals that you would like rendering correctly then you need to choose Silk.

If you've not already done so, you will also need to download either BasicLights.sh3f or
BacicPlusExtraLights.sh3f (As the name implies, the BasicPlusExtraLights also contains the BasicLights and adds lots of others) If you want to enable full light control.

I have 4 cores in my AMD phenom, but (as everybody knows) AMD fries a lot and so my PC shuts down often within rendering because the temperature on cores is too hight. [:((]

I used to have AMD, and yes they do get quite warm! [:(] If you are able to and are still using the stock cooler, you really should consider a 3rd party cooler, they make a big difference to temps. Even so it shouldn't be overheating and shutting down?? The computer should throttle the CPU to reduce temps, overheating and shutting down is usually only a last resort.

Have you tweaked the BIOS at all or are you using default settings?

Is the computer in a hot environment?

Is there a good air flow around the case?

I sell my photos for the prints. And a few months ago, someone bought a really big framed print of my "greek photo" (the orange waterscape on the first picture) so I was really curious how my photo may looks on someones wall. [:D]

Sounds great! [:)]

Thank you for the link.

db4tech