Raspberry Pi Troubleshooting

Check out Raspberry Pi's Troubleshooting Page for answers to questions such as:

• What is the username and password for the Raspberry Pi?
• Why does nothing happen when I type in my password?
• Why does my Raspberry Pi not start up/boot?
• Why is my Raspberry Pi hot?
• I keep getting a lightning bolt symbol and messages about power...
• My SD card seems to have stopped working.
• I've imaged an SD card with Raspbian/NOOBS, but when I look at it with my Windows PC, it's not all there!