Well, nothing on COM1 as far as I can tell, but with modern BIOSes and WinXP, it's kind of hard to tell.
|3lack|ce will be happy to know I finally decided to exert my consumer muscle and subscribe to a competing service, Verizon. Which, incidentally, provides the same service for the same cost, with better coverage, broadband speed, and (hopefully) stable client hardware.
I'll probably still noodle around with the Sprint card, since it's already been purchased, but I'm not too worried about it. I'll let you know if I ever figure it out.
Thanks everyone for your help!