Here's your one-stop thread on everything to do with your k750i and W800 phone, I've tried it:

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Advanced camera usage
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1 = Opens menu with "picture size" ready to select
4 = Toggles Macro mode (for close up photos)
7 = Toggels Night mode
* = Toggles Light (I also find this is the fastest way to use the light as a torch in the dark)
0 = While in video mode toggles length of recording.

Mute camera sounds; Before opening the lense cover hold # to toggle between silent mode easially.

Change brightness = < or >

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Secret Menus / Codes
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Service menu = >*<<*<*
Lock status = <**<
IMEI number = *#06#
Access contacts on sim card = Any nubmer then # (e.g. 9# to go to 9th entry on sim card.)
Phone status = Either volume button
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Free Downloads / Software
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Sony Ericsson Developer Tools (customise/design your own themes or remote control application)
HTML Code:
[Only Registered users can see links . Click Here To Register...] etc...
HTML Code:
Sony Ericsson - Sony Ericsson[....]c=en&s=10242_brands_files_Also search on eMule or BitTorrent (for downloading freeware only of course)

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Light up clock in standby mode
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Press the volume button

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Mute a phone call without rejecting it
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Press the volume button

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Hidden Smileys
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:-]
:-[
[:]

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Don't Drain The Battery
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With Lithium batteries there is no advantage to draining the battery. The battery will infact last longer with partial rather than full discharges. There is no battery memory effect with a lithium battery - you can charge the battery whenever you like without fear of reducing its charge capacity, and you do not need to drain a lithium battery completely before recharging it.

tnks it's a so good astuce

This is a loot of help

wow.. its working dude... awesome work..
btw.. how u got these? i mean.. did u experiment wit ur mobile>?

thanks for this useful post and help!
:-)

thanks....very useful

Great one im enjoying with this tricks.