Even though this guy is not a ham radio operator, the technology that he is using to transmit is similar to that used by hams, and so the remedies will also be similar. While there are measures that could be applied to the guy's transmitter (in addition to his not using illegal power) which would reduce the chance that his transmissions would interfere with your reception, it's unlikely that you will be able to fix things that way (a complaint to the FCC might possibly work, though).
Instead, you could look into adding some inexpensive measures (such as electronic filters) on your end to get rid of his interference. The American Radio Relay League (ARRL - www.arrl.org) referred to by the original poster has a lot of informative material that may help you. Some of it is on the web, and they also sell a book that goes into more technical detail on curing problems.
The problem is called "RFI", or "radio frequency interference". Here are a few web links that may help you, while a google search on RFI should bring up tons more: (it is possible that some of those links are only available to ARRL members, sorry if that is the case)
RFI Info
FCC RFI info
FCC Interference Handbook
The ARRL RFI Book
Thanks a ton for the info.
I don't want to bust the guy, but I'd like my AM radios and sound card to work properly.