If you format the drive you will clear the information from it and set it up as a new drive.
If the drive keeps reporting it needs to be formatted, then there may be a fault with the way the information on the drive is catalogued.
Do you know how the drive is formatted (NTFS, FAT, etc.) because you may need to know this to be able to get the information back off it.
You could try running CHKDSK /F on the drive, it will insist that you restart your computer so the tests can be done on a drive not in use.
If that doesn't work you may need to get a boot disk with some DOS based disk repair tools to try to connect to the drive and repair the way the information is stored.
I would recommend trying something called Recuva from
http://www.piriform.com/recuva
That will allow you to run a scan to see if there is anything on the drive you can get fairly quickly.
If the drive is reporting that you need to format it again, there might be damage done to the data on the drive.
Some of it might be damaged beyond recovery, some of it might need a little work to recover and some is completely perfect.
Give those tips a try and see if they help.
Cheers,