An external enclosure. 3.5" for the HD, or they have some that fit either a HD or an optical drive. Look through the deals section and you'll find some.
If you're planning to use firewire try to get one with the Oxford911 chipset. If you're connecting via USB2.0, then I'm not sure if there's a preferred chipset. Here is one that has the Oxford911 chipset, but it's 3.5" so I don't know if that's the size you're looking for.
I have one computer that has firewire ports, and two others that only have USB (pre-USB 2.0). So I wanted one with both USB and Firewire connections. I would also like to be able to put either a HDD or DVD±RW drive in the enclosure as well.
Technically yes USB 2 is backwards compatible with USB 1..but from experience its difficult to burn to a USB 1 drive on DVD media as the transfer rates just aren't fast enough. If the PC's don't have USB 2.0 you can buy cheap PCI cards for towers and PCMCIA cards for laptops to give you USB2.0
So it won't work too well with the DVD burner. How well will a hard drive work within the enclosure when plugged into a USB 1 port?
If I do get a USB 2.0 add-on card, what brands are good, and are there any brands that I should avoid? Are there any special features or anything that I should look for, or are they all pretty much the same?
Also, looking on newegg.com I see there are some USB 2.0 / IEEE1394 (Firewire) combo cards. Do these work as well as separate USB 2.0 and Firewire cards?
EDIT: I notice that some of these cards are advertised as having "internal ports". What are these used for?
The deal with USB1 isn't so much that it won't work outright just that the transfer rates are really pretty low and it gets in the way of what you're doing. A harddrive connected via USB1 will work ok just transfering larger files to it is going to take some time. If its USB2 you'd never have to worry about it as it'll more then keep up with the drive's write speed etc.
As for the cards a combo unit would be a good idea and really so long as there's driver support for which ever OS you're running they should all work more or less the same. The internal ports will be additional connectors that would allow you to connect extra USB or Firewire cables to. If your case has front USB ports for example you could connect those to the card to enable USB2 support on the front of the case (or firewire as the case my be)
So I could plug the USB 1 ports from the front of my case into the USB 2 card's internal ports, then the port would become USB 2? Or would I need to buy an additional port and replace the one on the front of the case?