My W850i has a white screen? Help?

[SeaMonkey]

Hi,
im new to these forums and have no experience of flashing phones,
but recently my w850i phone that i use for music stopped working.
whenever i turn it on it vibrates once and a white screen comes up and then vibrates again and stay with the white screen about half an hour later it just turns off.
ive tried taking the sim and memory card out the battery i charged it for at least 4 hours it still does the same thing,i connect it to my computer using usb cable and it doesnt do anything,i heard some people fixed it by flashing it and i came to this forum to look for some help.

i need to to know what to download and how to do it(tutorials) sorry if i sound demanding.

if you can help it would be appreciated
Thanks.

First read this 2 tutorials and when you first time connect your phone with XS++,post log from XS here without IMEI number
USB Flash Driver Installation - Guide - Top Sony Forums
XS++ 3.1 Guide-Flashing, Customizing, Recovering - Top Sony Forums