Asking for advice in upgrading Dell Studio 1557's RAM

[ErvinThomson]

Hi. My laptop supports a maximum of 8 GB RAM. It has already 2 x 2Gb DDR3 Samsung installed in it. From what I gathered by searching the net, I've found that 1557 has 4 places to install RAM in it and 2 of those are already filled.

Here is my goal:
Upgrading RAM to 6 or 8 GBs

Here is the problem:
- Studio 1557 has heating issues. The area around touch pad quickly becomes hot under moderate load. Also corei7- 720QM (which was one of the first i7s for laptops) becomes hot often.
- Worse than that, my graphic chipset burned about 4 months ago along with fan (I don't know which one caused the other). I had them replaced.
- So my 5 years old laptop has become quite unreliable (or has not?)

Here is my options:
1- Snapping in just 1 x 2 GB (so 1 slot would be empty).
2- Installing 2 x 2GB so I would have 4 x 2GB (all slots filled).
3- Staying out of this ill-fated mission since the machine is hot,old and unreliable.

What is the optimum course of action? What happens for Dual-Channel feature in cases 1 and 2? Does filling all slots cause too much stress for mother board?
I personally think this machine is going to work for me at least 3 years more so I like to add 2 x 2G GB (option 2).

extra info:
Memory Comments: 1333MHz, DDR3-1333 PC3-10600, 204p SODIMM, 1.5v

I'd really appreciate it if anyone can help me with this issue.
Thanks you

 

[ErvinThomson]

Update: 1557 has only 2 places to install RAM, so I have to replace the old ones with the new ones if I want to upgrade. I won't do it.