The ros laser is always near the drums. They are what images your drums. In the 800/1000 you work down from the top of the machine and find the lasers above each developer housing. Not sure what the config on a 700 is. Also, behind the top plate of the developer housing on an 800, you will find a little slot that contains a long glass piece that is between each of the lasers and the drums. That glass can get dirty, but I've never had it throw an error, just print quality issues. The lasers on 800s are a black box when looking down from the top and when you take them out, you can see the laser mech and glass cover on the bottom side that interacts with the drum. You want to used windex and lint free to clean any fog off any of the glass / mirror surfaces. But if it's giving you an error, it's either a bad laser or you just need to reseat all of the connections associated. Sorry I don't have much more info, I'm not familiar with the 700. They all work on basically the same premise, but the errors and configurations are different from machine to machine.