Why doesn't my bottom arrow key work?

It is not a hardware problem and easily solved by technicians. If you don't have enough knowledge than try with any Mac Book Expert. Mac Book technician will guide you step by step for reliable solution. Follow https://discussions.apple.com/message/24231664#24231664#24231664 and Mac Help .

Hi There,
Since you don't say which password doesn't work, I'm going to assume you mean the password needed to logon to the computer itself...
If you have the OS (operating system) install disks that came with the laptop, or a Mac OS install disk, you can start up from the disk by inserting it into the optical drive when the Mac is on; then restart and hold down the "C" key immediately after hearing the chime-sound.
-You'll need to hold the "C" key down until you see a grey screen with the Apple logo in it and a spinning 'pinwheel' below the apple.
Once your Mac starts from the OS installer disk, you'll see the screen for doing a new installation of the operating system.
Click on the arrow at the bottom right corner of the window that comes up.
Then, look at the menu bar at top of the screen and click on the "Utilities" Menu, and choose "Reset Password".
This will open a new window that is pretty self-explanatory as to setting a new password for the various Users that have been created on your Mac.
Hope this helps & good luck!

When the "save" dialogue box opens look at it carefully. There is a bar towards the bottom that tells you where your download will be saved. Use those arrows and select "desktop", which will save the download to your desktop, where you can see it. You can then move it wherever you want.

above the delete key. F12

should be a small hole on the door its a manual release. insert a paper clip the drive will open

When starting up the MacBook, hold down the option key. This gives you the choice of what disc to boot off of, if no drives show up, then your hard drive is corrupt and needs to be reinstalled. If the drive shows up, you can try booting off of it by selecting it and hitting the arrow. If this does not work, you can get your install disc out, comes with every Mac, and boot off the disk by holding the C key while starting up. After booting off the disk, you should be presented with the installer, pick you language but do not reinstall Mac OS X. Go to the menu bar and select tools, and then disk utility. In disk utility select your hard drive, and click repair disk. This should repair any errors disk utility found, now you can restart the computer and try again. If these do not work, you will likely have to reinstall your system.

did anything spill on your mac? Try blowing some spray air to clean in between the keys and keyboard. If that doesn't work, you can pop off the keys individually to see whats going on, but be very careful or take it to an apple store.

probably the operating system is corrupted . Try to boot with installation media and repair the disk permission and restart the computer.If it boot after file permission repair then its fine or else you have to format it.

open system prefrences and select network, select the "bean" along the bottom "assist me" and then select diagnostics, follow the instructions

Keyboards can range from $50 to $150+. Apple will probably charge under $75 for the install the new one. Check with a local apple store, or call 1-800-MY-Apple