If yours is like mine it has the option of doing either the whole page on the be or feeding it through the scanner. If you open the scan bed, there should be a little strip of glass to the left of the main pane of glass. That's the strip of glass that probably has the spot on it.

I'm only mentioning it because I get calls at work when scanners have these lines and this is the problem a vast majority of the time. One of the guys who services the scanners and printers showed it to me and it's been a helpful tip I never would have found it myself.

Theres a good example of what I'm talking about in HP's site here : http://support.hp.com/us-en/document/c01612462 You want step 3. Yours might not be an HP all-in-one, but it should look and function similar.

@Bobbo it's one of those all in one printers with a fax machine, and i figured it was the part that draws the paper, and it's probably my fault for using it to scan charcoal drawings a little while back. i took a look at it when it started doing that, but i didn't find anything, but i'll definitely look again a little closer. thanks!

is it a full page scanner or one that draws the paper through? If it is a draw the paper through type there is probably a single spot on the glass and that covers the scanning element. That one dot gets scanned over and over again as the paper is drawn across the scanner leading to a long line.

If it is a whole page scanner the problem is trickier to deal with.

Good luck