You will never be connecting those speakers directly to the computer, you will need an amplifier. But I don't know of any that are not meant for home AV, and will be dvd player sized with a number of inputs.
However there's another issue, it sounds like you had one of those all in one kits, so you'll need to check what amperage (measured in Ohms) usually 4 or 8 the speakers are, and make sure they match.
In the end you're either better off getting a new all-in-one kit, or a PC specific 5.1 speaker kit.