My recollection from using floppy disks is that they where notoriously prone to failure. Now imagine trying to read you old collection of disks not used since the late 1990′s. Before you run off collecting your disk and run fsck or let Windows try to repair them, you should consider your options.
Special disk controllers such as DiskFerret help in this task. By increasing the sample frequency and storing data for analysis, even aged disks can be read and restored.
A story of the usage of such a device, in combination with some nice vintage hardware can be read at Jordan Mechner’s blog. He wrote Prince of Persia for the Apple II, and now, 20 years later, the source code has been recovered.