My cd-key didn't work!

[Arto]

So after I installed M2TW , I played campaign , I made a gamespy account. I went to multiplayer typed everything in and I logged in... however there were no players out there so I filtered (People who play with 1.02 or 1.03 or a mod)
I saw lots of games , so installed 1.02 and immediatly after that I installed 1.03. So I log on.. dum dum dum dum! It says that I've an incorrect cd-key! WTF?! I typed the right cd-key in when I installed it and now! It won't work!
So... help please?

(Ps. If you're going to post this

You're getting the error message:
"Login failed - invalid CD-key"

Right this is how to resolve (with thanks to various posters)
You cannot change the cd-key ingame anymore (most likely for the protection against illegal games), so you have to do other things.

Open Start
Click Run
Type: regedit
Now go to this: "HKEY_LOCAL_MACHINE/SOFTWARE/SEGA/Medieval II Total War"

Now you'll see a value representing the CD-key. Change it to what it should be. You could have done the following wrong:
-Don't type spaces
-Do type the "-"s
-Don't use "o"s use "0"s
-Type everything (except for the numbers obviously) in capital letters

Now it should work, if it doesn't let us now ... preferably in the MP part

than I suggests that you would post screenshots or a video because I tried it (Maybe I made a mistake) and it failed.)

[AlfonsoVIII]

Is your CD key in all caps like this: XXXX-XXXX-XXXX-XXXX ?

[Arto]

Yes

[AlfonsoVIII]

If you swear that you entered it correctly, email me your CD key and I will try it on my computer. If not, uninstall the game completely and reinstall.