it said I can't update my phone to 4.0 coz there some modified software

[#1]

any idea???

[Nabeel · Accepted solution]

Its says so because your bootloader is unlocked.

You need to lock it

You cannot use PC Companion until you relock your booty

here is how

http://forum.xda-developers.com/showthread.php?t=1134335

or

http://forum.xda-developers.com/showthread.php?t=1324703

If you don't want to unlock bootloader then follow this guide