How can I change the memory to a more capacity one!?

Loraine Ramos, "memory because its almost full " sounds like you are talking about the hard drive and not the RAM. I suggest that you remove some of the documents/pictures/songs etc. that you may have stored. Copy those to a CD or DVD for storage. If you try to remove your hard drive and replace it with a greater size, you will have to reinstall your OS as well. So in order to give you a more precise answer, you will have to let us know if it is your storage memory or your RAM memory that you would like to increase. If it is RAM memory your computer supports:

Type 533-MHz, 667-MHz, and 800-MHz dual DDR2 unbuffered SDRAM, 256 MB, 512 MB, or 1 GB non-ECC. Maximum memory 4 GB. I suggest that you download the service manual from here. It will show you how to change your drive as well as your memory. Hope this helps, good luck.