E18 in the lower left corner of the screen and the view finder doesn't work

E18 is a lens error. You might try this repair technique:

Canon E18 Error

Click the "Start" button located in the lower-left corner of your screen.

Click on "Change your Windows Password" under "User Accounts."

Click "Remove your password."

Type your current password in the field and click the "Remove Password" button.
In Windows XP

Click the "Start" button located in the lower-left corner of your screen.

Click "Control Panel" and switch to the "Category" view on the left panel.

Click on "User Accounts" and then "Remove my password."

Type your current password in the field and click the "Remove Password" button.

hope this helps

That is shutter error code. I am sorry to tell you have to buy a new camera, it would be to expensive to replace.

The E18 error is fairly common on certain Canon models. Here's a link to information on what usually causes it and how to fix it. http://www.e18error.com/

Canon Powershot's error E18 has to do with the lens:
If it appears on a black LCD with E18 written on the corner, it is mostly due to the lens getting stuck while trying to extend. The camera will beep a few times and the LCD will display a little E18 in the lower-left corner. The lens gets stuck in the extended position, and refuses to move either to focus the lens or to retract when powered off.
I am giving below a link which will help you with E18 problem.

http://www.e18error.com/repair.html

Hope this helps, let me know if you have a proble.
Please do rate and thanks for using FixYa and Best fo luck to get you camera out of E18!

open it up then clean the lens
ben and peter jeffrey

Try lightly tapping lens on a hard surface. This sometimes reseats the lens. If this does not work take to bits and reassemble.

I won't say this is a solution but to prevent the lens retraction E18 message which seems to be common with Canon zoom lenses, I put the extension tube on mine. Sometimes I put a polarizer lens on it but usually I just leave it on to protect the lens when it is on. I have dropped it (on the carpeting at home) and never had a problem. If you have a Canon with a zoom lens, get a lens hood for it ASAP!! My wife's A520 has one on hers too. No problems.
There are lots of other places on the web with suggested fixes. Keep looking and keep enjoying this camera. Merry Christmas all.

Assuming you have tried the repair people on this site first, and need to follow it up further, I have found a site which gives some insight and proposes a fix if you would like to view it, it's at www.e18error.com They explain the problem like so:

Canon E18 error happens when the lens gets stuck while trying to extend. The camera will beep a few times and the LCD will display a little E18 in the lower-left corner. The lens gets stuck in the extended position, and refuses to move either to focus the lens or to retract when powered off.

Apparently, people who posted about this incident on forums say they had to send the camera for repair and that Canon has horrible customer support and response time.

They also say how you may be able to fix it yourself - which is nice - well worth a visit! Hope this helps

Perhaps the lens got bumped (if the camera was one when it was dropped) and is out of place. Mine did the same and I sent it in (it was within warranty) and Canon fixed it.