I want to install Retropie, (that's why I bought the pi) but lost the SD/MicroSD adaptor, so I would like to know if there is a way for me to install retropie using only the pi. thanks ahead of time!
Yes this is possible if Raspbian is installed on your MicroSD card.
sudo apt-get install git lsb-release cd git clone --depth=1 https://github.com/RetroPie/RetroPie-Setup.git cd RetroPie-Setup chmod +x retropie_setup.sh sudo ./retropie_setup.sh
But if you have nothing on your MicroSD card you have to buy a new MicroSD card adapter.