How can I format a 3 1/2 floppy containing data?

You can't 'format a 3 1/2 floppy disk that has data files written on the disc without loosing the data on the disc'

Depending on the format that was performed -
Quick format just distroys the 'File Allocation Table' which tells the operating system which sector the files are located
or
Non-quick format tries to remove all the data on the disk, but this is not always successful and the data can be recovered by using a data recovery program as below.
If you did not format the hard drive then the 'File Allocation Table' is probably corrupt and you should be able to recover the data as suggested below

PC Expert
March 2008

Don't all disks com pre-formatted these days?
Sounds like it corrupted

t
February 2008

This is a very odd question. First of all the answer is you can't format a 3 1/2 floppy disk that has data files written on the disc without loosing the data on the disc. (That is why you get all the warnings.)

I cannot understand how the diskette was loaded with data before formatting. It should not be possible. If there is any data at all on the diskette you may be able to recover it using a recovery utility. (Download from the www.)

If you need more, try a new question (this one will look closed) with some more information as to how you got in this situation. However my initial take is that there are no files on that diskette because it is impossible to write files to an unformatted diskette. (For example there won't be a Table of Contents (toc) area for the OS to write an entry into the toc to and so the write will fail.)

t
February 2008

'Formatting' a floppy disk destroys all data on the disk.

It may be possible to recover the data with a data recovery program which typically cost around $40 usd

http://www.jufsoft.com/badcopy/
http://www.floppy-recovery.com/

Bill
February 2008