talking about security code, how can i set the N900 to ask for a password/pin when the sim card is swapped/removed?

IMEI changing is illegal and for good reason and all those cloaked twisted reasons kicking around this thread that suggest a justifiable excuse to change a device imei are just ********.

People want to know how to do it for one reason only, to cheat the system. Ultimately that means someone who has lost their phone or had it stolen, loses out and I for one (who paid full cost for mine) do not support that.

I guess its makeable with the phoenix service software on older Nokia Phones. If it will go on the N900 - i dont know. Also there ist software for other vendors (Siemens) to change the IMEI. I Guess i saw such an option on the Nokia E70 and/or Nokia E90 via the phoenix service software.

no you're WRONG haider93
it only asks for imie so only people with n900's download it. its like capcha.
its not that easy to change imie.
do some reasearch before posting wrong things

You are quite near sighted to say things you don't know well too boldly. If a phone is reported stolen, its IMEI is locked, then changing the IMEI is supporting stealing. I have a different story for you to consider.

I bought a N95 operator locked to Softbank Japan. Softbank does not support Nokia firmware update. Elsewhere in the world the N95s are updated to 3.* firmwares but in Japan, the firmware for N95 just remain the same at 2.* version. I change the regional code to a non-softbank one, update to the new 3.* firmware, and get myself to a delema: the phone nolonger work with Softbank because all pre-configured things like useragent, wap setting for softbank are gone.

Failed to get setting information for N95 from softbank, I bought another softbank phone, a Toshiba T01a, which turned out to be a joke because the windows phone doesnot have english UI.

Frustrated, I put the softbank SIM back to the N95 to find out that its IMEI has been locked by softbank !! I made lots of complaint to softbank but cannot get my N95 IMEI back. So I send it to my country and a new IMEI is implanted in 5 minutes. (That's why I decided to stay away from any Japanese operator-locked phone and get myself a real treat, a N900, anyway).

In this island, even using a non-operator-locked phone is said to be illegal by those stupid japanese phone sellers. They locked my IMEI just because I bring it to them and by a new one from them!

I hope in my case, you don't see that changing the IMEI of MYOWN phone because it has been illegally IMEI locked by operator as illegal.

I am not a phone technician so I dont know how to do it, but I haven't seen any phone with IMEI impossible to be changed. Well, don't support stolen phones, but I love the idea of being able to do whatever you like with the product you own. I hate the idea my beloved one is being tracked. How many stolen phones have found their way back to their owners thanks to IMEI? So why IMEI?

Yes, IMEI changing is possible via service software such as Phoenix. As a user of nokia symbian phones in the past i had a similar problem as Duy2anh. My earlier cell, E55, was branded. Changed IMEI to general western EU region and was able to flash the phone with new firmware everytime. I'm i little bit sceptic about N900 though.

Hmm, it sounds like you have changed the phone's regional code, not the IMEI though.

As far as I can guess, Nokia use the regional codes because they pack their firmwares with different language pack for different region. Like if your phone has EU 1 region code, you dont have Chinese language packed in your firmware. Changing your regional code enable you to flash your phone to different language, and possibly different function, sometimes (like the FM transmitter in the N900 case.) Changing that regional code does not affect your IMEI at all.

True that. Now i recall it. Precisely as you say. But i remember i did change IMEI once couple of years ago on a symbian device. It is doable with some service software i did find on internet. Hell i even can't remember why i did it, it doesn't bring anything really. I guess experimenting.

Whether IMEI inside the device is changed or not, there is IMEI written under the battery. If the device is lost, it will be easier for a human to look at paper IMEI than to recharge the device to get electronic IMEI. If the device is stolen, thief will have to erase this paper IMEI, too, and any attentive/suspicious buyer will not like this and might (if he is suspicious enough) start an official investigation.

But I agree, changing IMEI is a shadowy activity. Not always illegal, but it's like: how can I make a plastic mask which would hide my face from passers by and look like normal human face?

Isn't the product code and not the IMEI what was used on Symbian devices to find new firmware versions?