These are flat out great speakers. The subwoofer delivers a solid bottom end and the satellites are quite clear. Most importantly, these are some very inexpensive speakers.

Installation
Very easy - plug the green plug into the front speaker output on your soundcard, plug the black plug into the rear speaker output on your soundcard. Plug the orange jack into the sub, plug the satellites into the sub, plug the power cord into the wall and you're set.
Then go into your soundcard options, set your speaker config to 4.1 (or 4 Speakers), and voila - 4.1 sound.

How's the Sound
The sound is very good for such an inexpensive set of speakers. (A like set from one of the 'top' makers will set you back around $200). The bass seems a little muddy, but turn up the sub's volume knob and it clears up. For best results place the sub up against your desk (or the wall). The satellites pack a good midrange punch as well as a very (but not quite crystal?) clear top end. Place the rear speakers in the right spot and a game like Aliens vs Predator 2 or Return to Castle Wolfenstein will make you jump. You really have to crank the Surround Volume knob all the way to get much from the rear speakers (I think that this is a 'percentage of the main volume' knob, although it doesn't say this anywhere).

Anyway
For $50 you can't beat the sound you get from these speakers. Definitely a worthwhile purchase.