floppy not accessible in a drive
 

I've been having trouble with "A" drive in Excel. I put in the disc to
update it with information and it will not retrieve any material previously
put on the disc and indicates "a drive not accessible - may be formatted for
macintosh"...then everything n my disc is gone and i can't access the "A"
drive anymore. What is happening here....what am I doing wrong.?

L. Findlay