Assigning a character to a function key

[Stephen Ronan]

Hi
I'm helping someone with a problem laptop. I've put 
Ubuntu-based Linux Mint on it, which is working well. The two 
major remaing problems are:
1) it's reporting lots of bad sectors on the hard drive
2) The "u" key doesn't work.

In regard to 1), I'm planning to use Spinrite, but am curious as 
to whether there may be any free programs that similarly can help 
with bad sector problem?

In regard to 2, is there a way to assign "u" to a function key? 
I'd be grateful for any advice on a good way to do that.

    Thanks,
Stephen Ronan