About a month ago, all six USB ports on our computer (Compaq Presario S3100NX) suddenly stopped recognizing anything we would plug in. We only use a few of them for our printer, MP3 player and memory drive. There is still power going to all of them. I can charge my MP3 player, but can't get it to work so I can transfer files to it. We've run virus and spyware programs and ever tried to do a system restore, but everything we try doesn't seem to get them working any better. Any suggestions on what might help?