ok..i serch and know only way to hard reset N900 is flashing with PC...but I think if we have an option like 3key reset on symbian it is very useful...

I dont know technically it is possible or not but if we fill form to request from nokia might be possible....

or not? anybody know?

The reset by pressing some keys is impossible on the N900.
Things have already been discussed

http://talk.maemo.org/showthread.php?t=43039

yes for now I know this is impossible but im wondering it is possible to add this for next update?

Try to add it as an enhancement request in Bugzilla. It will probably end in an INVALID or most probably in a WONTFIX, but it's worth the try.

If you do that, please post here a link to the bug page.

I think this is just technically impossible:

I don't know if I'm right:

But Symbian or WinMobile-Phones have a chip on which the OS is stored, which can't be changed by the OS. The so called ROM.
Hard-Resetting such devices means to delete all setting from a second storage - which can be edited.

The n900 is more like a PC in that way, which has a hard disk, and the OS changes "itselfs", manipulates files and the original state could never be restored as it isn't stored anyway.

You could not hardreset a PC either. You can just reinstall it from a CD - like you can reinstall you N900 from your pc (where the os is stored in a file).

Correct me if I'm wrong, but I think that's the way it is.

Bye
MPW

IMPOSIBLE is nothing but for this case there is no other way to do HardReset on the device lol. SO yes IMPOSIBLE.

Reflashing is the only way.