I've had a problem for quite a while where I cannot get the drive tray to eject, with or without a disc in the drive. Found that there is apparently some system contention going on (Apparently there's something stupid going on where pressing eject also signals Windows to try and read data from the disk at the same time it's trying to eject, which cancels the eject), there might be a better way to do this, but I've at least found something that works, most of the time, sometimes you still have to do this a couple times:

Open "My Computer", right-click on the DVD-RW drive icon, in the menu that pops up position the mouse cursor over "Eject" but DO NOT CLICK it yet! Now, press the eject button on the drive, wait a 1/4 second for the 'in use' light to come on, now as quickly as possible, click "Eject" in the menu.

Most of the time this will work. It's not perfect, but it's better than mindlessly pressing the eject button over and over.