I'm not real sure about this, but if you talk to the guys at Best Buy or Circuit City computer service counter (or maybe one of the guitar/pro sound shops), they probably can recommend a new sound card for your computer that has multiple mic inputs.
I do know they make battery powered inline preamps, but I can't say if that would be more cost-effective than a new sound card.
I do know they make battery powered inline preamps, but I can't say if that would be more cost-effective than a new sound card.