Ive cut a peice of plexiglass and i want to place it in an empty Optical drive slot. I used a CNC machine to cut an AMD design onto it. Iv left it slighly large so i can sand down as needed. I just cant decide what would be a good way to mount it and have it look good. I also will have lights in behind it. Any advise would be helpfull.

Here's an idea, if its not cut exactly to size, you could heat up the ends of the plexi and bend it at a 90 degree angle. Then drill holes and mount it that way.

If it is cut to size, you could probably use some epoxy and attach some small pieces of sheet metal to the sides with mounting holes drill into them and mount it that way.

I'll admit i'm no expert and I'm almost sure someone will have a better idea, but thats what I have to offer (how do you like that for self confidence lol)

I'm assuming its already pretty close to size so you can't just add some mounting tape to all sides...

One way would be to cut another piece of acrylic and have that sit behind the first piece. have the larger one attached to the case with bolts or mounting tape. Then you have a problem of how to attach the two pieces.

If there is enough room try to get some of the clear mounting tape and run that all the way around the edge of teh smaller piece. I don't believe that something like hot glue would work because it wouldn't really create a strong enough bond. If there really isn't enough clearance I would try the sheet metal idea or some other type of bracket attached to the sides of the acrylic.

If there is a bay cover next to where the acrylic will go, you could glue the edge of the acrylic to it.

You could fabricate a couple right-angle metal brackets to mount to the drive cage inside. Then drill holes in the corners of your plexi plate, and use chromed or powdercoated (to match your case) bolts to hold the plexi to the metal brackets. IMO this looks especially slick with countersunk allen bolts.

Or take one of the stock faceplates and cut out the middle of the face, leaving 1/4" or so all around. Then file down the plexi piece to fit inside, use glue to hold it, and mount the faceplate as you normally would.

BTW, one thing I've done is to use some reflective mirror film from an automotive supply shop. Then when the light's off, you just see a shiny silver surface, and when it's on, you don't even notice the mirror film is there.