If you are having a problem with the HTC MyTouch 3G Slide then you could perform a hard reset. By executing a hard reset your phone will reset back to the default manufacturer settings. This will means that all your data and setting on the device will be lost. If you have previously downloaded any softwares or ringtones this will also be lost. So before you do a hard reset make sure you back up your valuable data.
Note: data on SIM and memory card and will be preserved and will not be lost from a hard reset.
Note: if you phone is frozen and not responding just pull out the battery and put it back in after a few seconds.
Using the software menu method:
1. Press on the Menu key from the Home screen.
2. Next tap on Settings.
3. Next use your finger and slide the menu up.
4. Next select SD card & phone storage.
5. Then select Factory data reset.
6. Now select Reset phone. You may be asked to supply your password, put in the password when prompt.
7. Lastly choose Erase everything.
Now wait for MyTouch 3G Slide clean it self up.
Alternatively Try (from comments below):
1. Click the menu button.
2. click settings.
3. Go to Privacy.
4. Factory Reset.
Now wait for the reset.
Using the hardware key method:
1. First turn of the phone. Remove the battery and put it back if the phone does not response to your command. When pulling out the battery out wait for a couple of seconds before putting it back.
2. Next touch and hold on the Home + End key for around 30 seconds. When you see the Startup screen continue to hold down the key.
3. Let go of all the keys when you see a warning sign appears.
4. Next Press on Home key, then Power key.
5. Wait until the system start again and select Wipe data/factory reset.
6. Lastly, choose Reboot system now.
Your device should now go back to factory default setting.