I have a Dell XPS 720. I want to add USB 3.0 support to it, ideally on the front of the PC. Is this possible?
The built in media card reader is the 4th bay. Can I replace it with one of these? would it fit?
Yes it is possible. If you do not already have a USB 3 pin header on your mother board, you can apply hardware in the form of a PCI e cards that have 19/20 pin headers on the card, such as this as an example SYBA USB 3.0 External 2-port, 19-pin Header PCI-e Card. Look at specs needed, usualy a PCIe x4 up to x16 is needed on your board.
The "one of these" in your post is:
Yes it can fit in one of two ways:
This is designed to fit into a 3.5" space in your towere's front panel area. Your tower has two 3.5" panels and it would fit there if you have nothing else residing in these spaces.
If the "4th bay" is 5.25", you would need an adaptor bracket similar to this:
These can be made of plastic or metal and you can shop around for your prefrence.
2. 3.5-inch drive bays (2) Can hold an optional Media Card Reader or floppy drive.
3-6 5.25-inch drive bays (4) Can hold an optical or SATA hard drive in a 5.25-inch drive bay carrier.
NOTE: The hard drive carrier is only for use in the 5.25-inch drive bays. The floppy-drive/Media Card Reader and hard drive carriers are not interchangeable.
7 front panel LEDs (4)
8 optical drive tray eject button (4)
9 front panel LEDs (4)
10 power button
11 power light
12 computer stand
There are two ways to get USB 3.0 on an old PC without having to reach around the back side every time.
One option is to get a PCI-E USB 3.0 card, and then run a USB 3.0 extension cable or hub up to the front of your computer. This will probably be the easier option to set up, but maybe not as convenient to use. There are a lot of these available from online electronics retailers.
The other option is to get a PCI-E USB 3.0 card with an internal 20-pin connector, and then get a USB 3.0 faceplate for the front of your computer. This would fit into the spot where floppy drives went in older computers, and memory card multi-readers often go in newer computers.
I found a couple items on Amazon that would probably work; you might be able to find something similar for a better price elsewhere.
You can add a third party USB 3.0 card to an open PCie slot Startech makes several and there are others. Most will want power from a SATA power conenctor.