Floppy Drive

I work at a library and here we are running windows 2000 on dell gx100. the problem is that sometime the floppy drive takes a long time to read the diskettes and sometimes it cant read them at all. I know i read somewhere here about a jumper that might be set wrong or something.anyways I sometimes get the disk needs to be formatted, even though it had read it fine in an earlier occasion. Can any one tell me what the problem might be?
thank you