I recently purchased two 2GB Crucial RAM, but when i put it on the laptop and try to turn it on, the computers starts making 3 beeps then the blue lights stay on but the laptop wont start... what can it be? (works fine with original 512 ram)

You have purchased the wrong type of memory or one of the memory sticks are bad.
Try inserting just one at a time.
If the same problem, re-install the orig. memory and replace the purchased memory.

Check your board manufacture spec. Some boards only accept up to say 1 Gig ram or (other) the beeps are reporting that it does not like the amount of ram or type of ram, ensure you have purchased the correct clock speed etc according to your board as well. Hope this helps

Do you tried to tell to an supplier of the PC?
Try to tell and follow all the instructions.
Peace!