Ok since there is a lot of conflicting answers...
The X-530 is designed to be used with surround sound cards, and only those cards. If you want to use it with a standard stereo card, you can only plug in the front inputs into your card and use the satellite speakers. Note that this most likely will not give you the sub as I see no indication that the sub is crossed over on the front speakers when not directly connected.
You can also split your stereo out of your laptop, but in general this is something i would avoid, most computer speakers sound crappy enough that you wouldn't want to add in phasing issues by running the same signal in to both front and rear speakers, just use the front. I also am not completely sure that the sub has a crossover in it as opposed to expecting a proper already crossed over signal, so this wouldbe really bad for the sub.
So in all, can they be used? Yep, but you may as well get a 2 speaker system at that point because that is all you will be hearing.
And for the record, for most people it will be the front left and front right speakers they would hear, not 1 speaker and a sub. Could you get this setup if you tried? Certainly, but as mentioned before, unless the sub is crossed over correctly it would not only be a bad idea for losing any sort of stereo image, but bad idea as you could damage your sub. And of course the fact you wouldn't be sending a good signal for the sub of the left channel by sending the right to the sub, means it would be a sub-par mono system at that.