For about 2 weeks now, there has been this one vertical line on my computer that will NOT go away. It only appeared after I turned it off, and turned it back on the next day. This morning I turn it on and now there is another vertical line. What can I do to get rid of it?

It's possible that your screen is broken. You should consider buying a new monitor. Look for plasma screens instead of LCD.

If you are using a laptop, use constructor guarantee. If you don't have any guarantee, you will have to buy a new, external monitor to use your computer.

If you have access to another monitor, hook that up to see if still vertical line on another working monitor.

If you have access to another computer, hook your monitor up to it and see if line is still there on another computer.
-If there on another computer, would be time to maybe replace the monitor

These are just some steps to try and narrow down if monitor itself or possibly something else