If you already have the latest patch (which you should!), you shouldnt need to edit any files, with the latest patch, the button 'T' is defaultly set to 'Talk'. If you have messed with the keyboard configuration or that you dont have the latest patch, you will need to edit a file. The file is called 'user.ini' and it is in your system folder of your deusex root folder (ie, C:/DeusEx/System). Open this in any Text editor, notepad should be alright. Once opened, search for 'T=', this should be in a section called '[Engine.Input]'. Once found, you need to edit its value to 'Talk', to do this, after the =, type 'Talk', so it should now look like this:

T=Talk

Now go into the game, press the 'T' button. You will see the followong at the bottom left of the screen:

>Say

You will need to press backspace till you remove the 'Say', so its just '>' now. Now you will need to type the following:

Set DeusEx.JCDentonMale bCheatsEnabled True.

Now press enter, nothing will appear, but you have just activated cheats. Because you will need to redo this for every level, you can open up 'user.ini' and add 'bCheatsEnabled True' in the [DeusEx.DeusExGameInfo] section of the file to allow cheats to be activated forever.