Use my method mentioned above, charge phone until 100% and unplug from power supply, then leave it in sleep mode for 2-3 hours. (DON'T turn on screen or use the phone at all during sleep mode)
After 2-3 hours, please screen capture on battery status something like this (if activities more than 1 page, scoll down and screen capture activities below):-
http://i1248.photobucket.com/albums/hh493/...zpsa618b7cc.png
From battery status screen, you know which activity drain most of battery. For my case, you can see after 2 hours+ in sleep mode, the battery drain about 2%. This means battery and firmware work fine and normal, so if battery drain fast is purely from usage pattern.

Please screen capture your phone firmware too like this:-
http://i1248.photobucket.com/albums/hh493/...zpsec00f301.png

You need provide more information before members here can provide more appropriate solution. Battery drain very depend on your usage pattern. If you turn on screen every 5 min, automatic upload data at background through WIFI/3G, play HD game, etc.. All these activities will drain your battery faster.

What is your phone firmware?

If your phone running GB, then press and hold "Power" button for 2-3 sec, a screen will pop out, select "screen capture" to capture a screen.

If your phone running ICS, then press "Power" and "Volume Down" buttons at same time to capture a screen. This one a bit hard, timing very important, press both buttons at same time, if press either one button faster than another one, it won't trigger screen capture.

Boot your phone. When you see LED light in blue color, repeatedly press back button to enter CWM.
Select the option to wipe data/factory reset.

Actually, I'm not quite understand what you tried to describe your problem.

No. you can use any brand of 3.5mm earphone/headphone.

Do you try with another earphone? same problem? (Borrow from friend if you have 1 set of earphone only).

Do you try on Music Player? same problem?

The 3 rings for microphone + stereo audio, while 2 rings for stereo audio only. I think your 3 rings earphone used CTIA/AHJ standard while Sony Ericsson 2011 Xperia series used OMTP standard. If you plug your 3 rings earphone to iPhone or HTC phone, it should work well.


Attached thumbnail(s)

Yes, agreed. Both RAM and internal storage are low.

If the phone rooted, internal storage not an issue if use Link2SD or similar apps. I used swap method to reduce lag when phone running low RAM.

If use stock firmware without root, not much apps can go in this phone.

You can refer to this website: http://forum.xda-developers.com/xperia-arc
You can get a lot of guides how to root or install custom ROM on your phone.