There are a lot of system images piling up on my disk in the android sdk folder. i hardly use the emulator. May be once in 6 months. Most of my development
By deleting all emulator, sometime memory will not be reduce to our expectation. So open below mention path in you c drive
C:\Users{Username}.android\avd
In this avd folder, you can able to see all the avd's which you created earlier. So you need to delete all avd's that will remove all the unused spaces grab by your emulator's. Than create the fresh emulator for you works.