Dell sk2305 @

By holding down your Function key (Fn) and pressing your F2 key you turn your wireless card on/off.

Your Function key is on the lower left hand corner of your keyboard, next to your Windows key and your F2 key is in the upper left corner.

Try ALTCAR (the right ALT key) +2

it shows that the @ key on keyboard may gone bad, if the other key is working then you need to change the keyboard setting from control panel

Should be located in the upper right hand corner. It may be highlighted in blue letters, meaning that you have to use the blue <FN> key next to the space-bar to imitate it.

Do you mean the " symbol?
by "upper case" do you mean when you press the shift Key?

if the answer to both questions is yes, then the keyboard is working correctly
.

If you are typing using the touchscreen, the upper-case arrow, touched once, will upper-case the next letter you type and then back to lower case. It you touch the upper-case arrow twice in a row, you should see a green light come on directly over it. That keeps the caps lock on.
If you are using the slide-out keyboard, touch the upper case key once and you should see a triangle underneath the cursor on the screen. That will upper case the next letter you type. To get it to stay in upper case, hit the upper case button again and the triangle should change to a > symbol, point up, underneath the cursor. That should keep it in upper case mode. Don't hold the upper case button down, as that won't do anything. A third press returns it to normal (lower case).

Try this, "Start" "run' type in "regedit" then ok, in the left field click the "+" next to "Hkey_Local_Machine" + next to "System', + next to "CurrantControllSet", + next to "Control", + next to "Class", then click on {4D36E965-E325-11CE-BFC1-08002BE10318} then in the right field, right click on "upper filters" then delete, right click on "lower filters" then delete, restart pc. See if this works for ya.

use your upper case i for lower case, and a upper case i and an underscore for the upper case I_etter.

This means the number lock is on - in the upper right hand corner of the keyboard is a series of 4 keys.  Far right is delete, then (from the right) insert, Prnt Scrn, and Num Lk.  Hit the Num Lk key, and the number 9 with the padlock should shut off.  Your keyboard should now work normally.  
Any more problems, let me know!

Turn on (or restart) your computer.
When F2 = Setup, F12 = Boot Menu appears in the upper-right corner of the screen, press <F12>.
The Boot Device Menu appears, listing all available boot devices. Each device has a number next to it.
At the bottom of the menu, enter the number of the device that is to be used for the current boot only.

If this works and you want to change the setting permanently do the following:
Turn on (or restart) your computer.
When F2 = Setup, F12 = Boot Menu appears in the upper-right corner of the screen, press <F2>.
Use the arrow keys to highlight the Boot Sequence menu option and press <Enter> to access the menu.
NOTE: Write down your current boot sequence in case you want to restore it.
Press the up- and down-arrow keys to move through the list of devices.
Press the spacebar to enable or disable a device (enabled devices have a checkmark).
Press plus (+) or minus (–) to move a selected device up or down the list.