RAM missing

So yesterday I noticed my laptop was running slow. I looked for a bit and found that the resource moniter was saying that 4GB was hardware reserved (out of 6gb). I didn't do much because I was busy.

Today when I turned on my laptop I see that the resource moniter only says I have 2GB of memory avaliable. I check the bios and it also says that I have 2GB of memory.

I'm thinking that some of my RAM may have stopped working (my laptop is over 3 years old.)
Am I correct in thinking this? Do you guys know of any possible other explanations?

I kinda don't want to take apart my laptop until I know for sure the RAM is broken because it looks like a pain.

Thanks!

Usually there is an access door or panel that covers the RAM modules. It's only two or three screws to remove it. Unplug the power pack and remove the battery before you open it up. You don't want it accidently starting up while your working on it. Take precautions against static discharge too. If you gently move the retaining clips to the side the module should just pop up. Then you can carefully remove it to get at the one underneath it. Then carefully reseat them back in. If that doesn't fix it you have a bad module or a motherboard fault.

Thanks! Reseating them worked. memtest came up clear too so thats good :)