My phone(Nokia 5310) says that the memory card must be formatted so I click yes. Then it says it must delete everything from the memory card so, again, I click yes. It says formatting memory card then it stops and says operation failed.

Try and format your memory card using a nokia phone in its memory card manager,it will work.

you can use the Nokia 5310 for many different storage and entertainment functions. The mobile phone has the ability to save all of your large files (such as pictures) to a memory card instead of using up all of the built-in device storage. You may run into issues with the memory card if it is locked. This can happen if you buy a used card or if you forget the password that you programmed into the card at the time of purchase. You can unlock the card with a default password, or you can delete the option that requires the memory card from requiring a password at all.

Instructions

Unlock the Memory Card

1. Power off the Nokia 5310. Put the memory card into the memory card slot on the Nokia and then power on the device.


2. Click the "Menu" key down from the main screen of the 5310. Select the menu option for "Extras."


3. Navigate the cursor down to the bottom of the page. Press down on the option for "Memory Card."


4. Click the "Options" selection that appears as a screen prompt. Move through the options until you reach the "Unlock Memory Card" option. Click the cursor to select the "OK" option.


5. Manually enter in the unlock password with the 5310 keyboard in the password box. When you cannot remember the password, the generic passcode is "12345" or "1357."


Delete the Memory Card Password

1. Power off the Nokia 5310. Put the memory card into the memory card slot on the Nokia and then power on the device.Click the "Menu" button down from the main screen of the 5310. Select the menu option for "Fun & Apps."


2. Scroll down to the selection for "Gallery" and then press on the "OK" key. Navigate to the "Memory Card" screen selection and then press on "Options." Move through the list until you reach "Memory Card."


3. Press down on the option for "Delete Password" when the screen pop-up menu loads. Verify that the words "Memory card will unlock now, do you wish to proceed?" appears. Select the option for "Yes" to verify the unlocking.


4. Navigate to the password box and manually type in the default passcode. When you cannot remember the password, the generic passcode is "12345" or "1357." Select the "OK" key when you are complete to remove any passcode requirements from the 5310.

to unlock memory card insert memory card in ngage mobile and format the memory card

recovery of memory card is not possible

Delete some unnecessary files in your phone memory like images and videos. Go to your phone gallery and delete some of those. And if you want to use the memory card as phone message storage then go to Messaging - Option - Settings - Other and then Memory in Use, select your memory card.
But if your phone is infected with a virus then you need to format your phone. One sign of infection is your phone keep sending a message randomly from your contacts without your consent.
Use these code and enter it to format your phone:
*#7370# and then the default code is 12345.
thanks

Yes dude its very simple!
You have to go to the market and buy a new memory card...
That All you have to do...

Got it???

yes put your phone card in a card reader and once it shows on the computer right click there and click on format once it fromatted you all data will be lost but you can reset your password

first pdate ur phone using nokia software updater..so everything in ur phone will be new...then after updating...put the memory card in...it will ask for passowrd..ignore it...then go to memory format it...after formating...u can see there is a set passoword...set is to 12345...after setting there will be a new password...then after thats done...remove the password with 12345...then everytihign will be done...ok.

The e-mail solution posted by Nokia below to unlock the media licence keys after firmware update worked and is thus (Note all your phone music will be wiped so will need to upload again from your PC):

1. Connect your phone to Nokia PC Suite in "PC Suite" mode. Launch PC Suite.
2. Use PC Suite Content Copier to back up the contents of the memory card onto the PC.
3. Disconnect the phone and format the memory card:

Menu > Gallery > (the memory card folder) > Options > Format memory card > Yes.

4. Re-connect your phone to PC Suite and restore the backed up data to the memory card.

you can't, unless you re-format the card. This will lose any data that you have stored on it.

If you have got the software for your computer for the phone then you ca right click the memory card from within the software and click on format.

Other to that you can by an adapter for the card to fit into the usb port on your computer,(they are relatively cheap), then go to >My Computer and right click on removable device (the one with your card in), and click on format.

I hope this helps

http://nds1.nokia.com/phones/files/guides/Nokia_5310_Xpress_Music_UG_en.pdf
Have a look at your manual page 35 for instructions
(Some supplied memory cards are preformatted; others require formatting. When you
format a memory card, all data on the card is permanently lost.
1. To format a memory card, select Menu > Gallery or Applications, the memory card
folder , and Options > Format memory card > Yes.
2. When formatting is complete, enter a name for the memory card.)