Well, if you copy a "bad" config.sys file to the C: drive of a desktop computer, you're hosed until and unless you can boot the desktop computer from another drive and remove the offending config.sys file (MS DOS 6's new F5 bypass key feature notwithstanding.)
Unfortunately, on the Zoomer, you only have two choices. A soft reset boots from the B: drive, and a hard reset boots from the A: drive. There are no other options that I can think of.
So, in answer to your question... unless someone can think of a creative way around it, I think your only option is to hard reset to remove the misbehaving config.sys from the B: drive.