If the USB drive is NTFS, some versions of KNOPPIX will not write to that. Here's a distro that might -> http://www.inside-security.de/insert_en.html
I have a Windows Media Center system that won't boot. I was going to boot up KNOPPIX and copy important files from the C: drive to en external hard drive, then reinstall Windows. KNOPPIX comes up ok and sees my USB drive but when I try to copy files from the C: drive to the USB drive the 'Copy Progress' window comes up and just sits at 0% forever. The USB drive is mounted and accessible. I am a KNOPPIX newbie and would appreciate some assistance. Thanks.