buzzing feedback on hard drive recording

[mapenni]

I am a court reporter taking depositions in a variety of locations. I use an external mic to recorder the room on my hard drive while I am taking the deposition so I can double check it when I proof read it. There are some locations where I get a terrible buzzing feedback on my recording. It's so loud that I cannot hear the people in the room. I plug the computer into a wall outlet with a surge protector. I am using a high gain microphone plugged into the mic jack on the computer. I am using Windows XP. This only happens in some locations, so I am thinking it is location dependent. My software company suggested I buy a new surge protector (which I have done) because it could be caused by improperly grounded outlets. I can't really test this because I need to be in one of those rooms where it happened before to recreate the situation.

Does this sound reasonable? Will a surge protector eliminate the buzz if it is indeed from improper grounding? Could my old surge protector be worn out?

This is making me nervous because I use the room recording during a deposition to read back questions and answers to the attorneys. If I can't hear it, I'm toast.

Thanks for any help anyone can give me.