There are 2 things going on in your dream... your mom gives it to you and then takes it away AND you discover that your girlfriend has another email address. So, there are 2 key dream symbols at work in your dream.
Here are links to the definitions of
computer:
dreamdoctor.com/computer/computer.html AND
email:
dreamdoctor.com/letter/letter-email.html
If you click on the link at the bottom of each symbol definition, it will guide you to its meaning.
How you felt IN the dream (angry, disappointed, worried, etc.) is how you feel about its subject in your waking life.
Without knowing the waking life background which generated your dream, it seems as if the dream is about your communication/miscommunication with your girlfriend and your parents approval of that communication and/or relationship(?)
Hope that helps!
