ok every time I turn my mac on a black line the size of an ipod touch appears in the right side of my screen.I can't tell what it is I tried to get information on the internet but it looks like there is nothing.Also the line is vertical and covers from top to btn. And I dont have the mac cd.(The Pc is an IMac)

Sounds like a damaged monitor.

Does it do this when you're booted from an alternate media, like the install/restore DVD? Or does it do it in ALL user accounts, or just a specific one?

It happens when I turn the computer on no matter what user

Sounds like a damaged monitor. Is it under warranty?

Yes but i dont think its damaged 1rst because ive had the mac 4 2 years by now and I got the line ever since 1 of my friend's came to see a movie at my house and she turned the mac on and was playing with the kbrd I dnt know.Is there a command to do that,or 2 fix it?

Does the line show up in a screenshot image (command-shift-3)? Can you take a picture of it and post it here so we can see exactly what you're talking about?

If it is indeed monitor damage, well, the damage has to happen at some point -- it's not unlikely that a 2-year-old computer would suddenly get monitor damage at the precise moment your friend watches a movie... although I'd have to see a picture of it to determine whether it's damage or some setting gone wonky.

nope if I take a pic directly from the mac, it's invisible

Even more evidence that it's a damaged monitor, unfortunately.

Next thing to do is boot from something other than the hard drive, say, your Mac OS X Install/Restore CD/DVD. If it does it there, too, then it's almost certainly a damaged monitor.