Hiaig posted it before me.
"adb devices" will let you check if your device is properly connected for adb to work.
"adb remount" to mount it.
and the push command to... well, bring the build.prop into your /system folder
It is interesting for you as well that, in case you couldn't get the build.prop through the graphical interface, you can still obtain it through adb.
Try
Code:
adb pull /system/build.prop build.prop