So...if i put 4 gb of ram in a machine that can only handle 3gb .

Yea i ordered myself some new ram for my Macbook . Its one of the old ones.  here are the specs 
 
2ghz Intel core Duo
1gb 667 MHz DDr2 SDRAM
 
 
Well there the basic specs anyway
 
SO i read online that they can only be upgraded to 3GB but i bought 4 GB  from crucial
 
x2 ddr2 2GB
 
SO ... my question is if i put both in what happens . Nothing or something ? just thought you guys could help me out .
 As you can guess im not really all that great with computers so please hold the sarcasm

Nothing, you'll just have a useless GB of RAM.

 Or it will create some sort of black hole that will engulf the universe. Good luck. "

" @Mikemcn said:

 Or it will create some sort of black hole that will engulf the universe. Good luck. "

so, we're doomed then?  "

Don't do it, your CPU will heat and be destroied.

I have 4gb on vista 32bit and it only recongnise 3gb but it doesnt really matter :P

The older core duo macbooks only support 2GB. The "updated" version of that older macbook that has a core 2 duo can support 3GB, so if you happen to have that your system would just ignore the extra gig. If you do have the older one like you say the second 2GB stick will be ignored.  
 
I found this out the hard way when I upgraded my core duo macbook a month ago. 

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!

nothing will happen, the computer will only recognize the 3 gigs and the 4th one will only take up space.

Maybe you mean the 32 bit operating systems like vista 32bit. It would reconise 3.5 gigs at least even if they advertised it to 3 gigs.

Just send that 2gb stick my way =P