2. Ensure that the computer and all attached devices are turned off. If your computer and attached devices did not automatically turn off when you shut
down your operating system, press and hold the power button for about 4 seconds to turn them off.
Inside View of Your Computer

Vostro™420

Vostro 220

Vostro 220s

1
power supply
2
5.25-inch drive bays (3)
3
media card reader (optional)
4
I/O panel
5
3.5-inch hard drive bays (4)
6
chassis fan
1
power supply
2
5.25-inch drive bays (2)
3
media card reader (optional)
4
I/O panel
5
3.5-inch hard drive bays (2)
6
chassis fan