CD-ROM drive button is loose- broken?

An "Expansion Bay" is a bay or a tray if you will that is spare so that you can fit a device into it like a CD/DVD drive as well as some specialised items.
Being that its a HP could be that it's for future use due to matching the color, assuming that it has another dvd drive fitted or it's also possible that one was not fitted at all and that's the reason the button does nothing.
Click on the start orb, select Computerand click on it, it will display all the drives, see if there is a CD/DVD drive showing. If not, I would be getting onto HP prontoand making a big noise.
Never mind the drive isn't expensive, it's not the point, it should be there and working.
They save millions by people not complaining about minor problems because frankly it's easier and quicker to do it yourself.

Here's what it says under Devices with Removable Storage

DVD RW Drive (E)
Removeable Disk (F)
Removeable Disk (G)
Removeable Disk (H)
Removeable Disk (I)

In that case it looks like the drive has a faulty switch. Easy enough to replace, brand wise these days they are much the same. You can get a dud in any of them occasionaly.
I've had a good run with LG, when I got my first SATA DVD drive they only had Lite On so I got that, guess what, it was faulty, it could only read cd's not dvd's. I got it replaced the next day and now it's working great.

do you think you could recommend a drive for me that could play CD's and DVD's, something like a universal drive? Thanks !

i found this one, will it work for my computer?

http://www.amazon.com/gp/product/B002HFWBIA/ref=ord_car...

Yes that will do fine.