Well, standard trays opticals, the disc will fall out if you mount it sideways. U will have to buy one that has latches, or a trayless load.
Actually, I believe most optical drive trays should have little tabs to hold a disc in place. Checking the drives around here, the only one that doesn't is an old CD burner from the late 90s. You'll notice them on each corner of the tray, if they are there, which they probably will be. They are tiny, but should be all that's needed, since the back of the disc remains a bit in the slot to keep it from tipping out when open, and the disc is locked into a spindle and not even touching the tray when in use. You might want to test with some unimportant discs first if there's any question about it though.
It would be less likely to damage the drive than if its' turned on its' side.
Lot's of prebuilt computers have their drive mounted vertically. In fact, even many external enclosures are designed to be positioned either way. Orientation is not likely to have any significant effect on a hard drive. I would be much more concerned about having the drive in an enclosure, as it's more likely to get knocked around that way.
I actually have one of my less-used computers turned on its side, and it works just fine that way, optical drive and all. It does look like the sides of your N200 case bulge out a bit, so I'm not sure if that could potentially cause any bending with a lot of weight resting on them over time. You should probably put some feet on the case though, so it won't be sliding around on your desk and scratching up the side, and to keep fan and drive noises from reverberating. I just used some small stick-on rubber pads that I had around. If the existing feet of your system are removable, you could even use those if you can find a way to attach them.