though like Desdendelle said, it depends on what computer you have. I know that on my laptop, the cover for the 'x' key occasionally pops off because the cover for the 'z' is totally gone, thus affecting the 'x' key( but it still works since it's pressure sensitive and all that). The key-cover has a little plastic doohickey on the back that snaps down into place over the actual button for the key.

As for scrolling on a track pad, try going along the right-hand side of it with one finger. That's usually where they put the scroll function for PCs. Also, you can use the 'page up' and 'page down' keys if you absolutely need to. It's clunky, but it's there.

On what sort of computer you have. Also, by trackpad I assume you mean something like this?