How to hard reset xperia c1904

hi there.
not sure if this is your phone as you did not give model number.
but try this.
First method:

1. In order to switch off the phone hold down the Power button for a short while.
2. Afterwards go to Settings and then to Backup & Reset.
3. Then selec Factory Data Reset and tap Reset Phone.
4. Choose Erase Everything if you are sure you want to clear all your data.

More items...

SONY Xperia XA F3113 - How to Hard Reset my phone - HardReset.info

www.hardreset.info/devices/sony/sony-xperia-xa-f3113/
or this one.
Restarting andresetting your device Sony Xperia XA support Canada English
or this.
Restarting resetting and repairing Sony Xperia XA support English
or this.
SONY Xperia XA F3113 How to Hard Reset my phone HardReset info

Please do check the Phone Ringtone
If the ringtone file is missing this may happen

Try change another ringtone (This option may be available under volume settings)

This link might help.
How to Unlock Locked Cell Phone and Why You Might Want To

restore settings

or this one note all data will be deleted

How to Soft Reset or Reboot or Restart SONY XPERIA T LT30p ?
To soft reset SONY XPERIA T LT30p, press the POWER BUTTON KEY for several seconds, we will see the menu to restart or turn off. Choose restart/reboot than the SONY XPERIA T LT30p will do the soft reset or restart. This is safe to do because non of important data or applications will wipe or erase.
#Option 1, Hard Reset SONY XPERIA T LT30p with Software Menu :

1. Make sure the battery is charge properly
2. Turn on SONY XPERIA T LT30p smartphone
3. Don't forget to backup all important data
4. Go to menu: Setting > Backup & reset > Factory Data Reset > Erase internal storage > Reset Phone
5. Choose Erase everything to continue and confirm you ready to do the format SONY XPERIA T LT30p
6. The SONY XPERIA T LT30p will continue the step until ready to use in clean factory default.

#Option 2, Hard Reset SONY XPERIA T LT30p with Flashtool applications:

1. Flashtool in the applications from Sony can be download from Sony website.
2. Flashtool software need to installed in you computer and ready with USB data cable
3. Make sure SONY XPERIA T LT30p battery is charge properly or full charge
4. Power off SONY XPERIA T LT30p
5. Boot SONY XPERIA T LT30p to flashmode with using: Volume Down Button and connect to USB cable at No.1 above
6. Follow the menu at you computer display, it is easy to understand the steps.

#Option 3, Hard Reset SONY XPERIA T LT30p with Hardware Key Button:

1. Make sure the battery fully charge
2. Do not forget to backup all important data
3. Turn off the SONY XPERIA T LT30p
4. Press and Hold together: Power Button + Volume Up Button for several seconds
5. Follow the menu at LCD screen to continue the hard reset SONY XPERIA T LT30p

You can choose the step options above to do hard reset while the SONY XPERIA T LT30p get problem or not running well. But we always suggest to do routine backup before your smartphone get problem. If SONY XPERIA T LT30p already stuck or run slowly or not responsive, then better try to do backup as you can because all important applications will be wipe or removed from SONY XPERIA T LT30p after doing master reset, but some data which saved at memory card will be safe, better to remove the microsd memory card before doing the hard reset.

http://www.hard-reset.org/factory-default/how-to-easily-master-format-sony-xperia-m-c1904c1905-c2004c2005-dual-with-safety-hard-reset/
Hope this helps.
You installed anti virus?

To soft reset SONY XPERIA T LT30p, press the POWER BUTTON KEY for several seconds, we will see the menu to restart or turn off. Choose restart/reboot than the SONY XPERIA T LT30p will do the soft reset or restart. This is safe to do because non of important data or applications will wipe or erase.

solution 1, Hard Reset SONY XPERIA S LT26i with Software Menu :

1. Make sure the battery is charge properly
2. Turn on SONY XPERIA S smartphone
3. Don't forget to backup all important data
4. Go to menu: Setting > Backup & Reset > Factory Data Reset > Reset Phone
5. Choose Erase everything to continue and confirm you ready to do the format SONY XPERIA S
6. The SONY XPERIA S will continue the step until ready to use in clean factory default.

solution 2, Hard Reset SONY XPERIA S LT26i with Flashtool applications:

1. Flashtool in the applications from Sony can be download from Sony website.
2. Flashtool software need to installed in you computer and ready with USB data cable
3. Make sure SONY XPERIA S battery is charge properly or full charge
4. Power off SONY XPERIA S
5. Boot SONY XPERIA S to flashmode with using: Volume Down Button and connect to USB cable at No.1 above
6. Follow the menu at you computer display, it is easy to understand the steps.

solution 3, Hard Reset SONY XPERIA S LT26i with Hardware Key Button:

1. Make sure the battery fully charge
2. Do not forget to backup all important data
3. Turn off the SONY XPERIA S
4. Press and Hold together: Power Button + Volume Up Button for several seconds
5. Follow the menu at LCD screen to continue the hard reset SONY XPERIA S

Be careful before doing this step to master reset, because all important data and applications will be removed from SONY XPERIA S, we always suggest you backup all important data before performing the hard reset.

http://www.sonymobile.com/gb/tools/update-service/
click on Download update service
follow on screen instructions, to erase and factory reset phone.

Heres how to reset without access to the phone.

1. Turn the power off. If your Sony Ericsson Xperia X10 is frozen, pull the battery out and reinsert it
2. Hold the Left and right buttons located beneath the display
3. Press and release the Power button
4. Follow the on-screen instructions to hard reset your Xperia X10

All data including third-party applications will be deleted from the Sony Ericsson Xperia X10. Once the wipe is complete, the phone will reboot to its factory fresh state.

Good Luck, second time someones asked for this model tonight so i had answer on hand!

Try entering the password null. If it doesnt worked means try to do a hard reset .

1. Turn the power off. If your Sony Ericsson Xperia X10 is frozen, pull the battery out and reinsert it
2. Hold the Left and right buttons located beneath the display
3. Press and release the Power button
4. Follow the on-screen instructions to hard reset your Xperia X10

All data including third-party applications will be deleted from the Sony Ericsson Xperia X10. Once the wipe is complete, the phone will reboot to its factory fresh state.