If you want to use Turkish letters 'ç, ğ, ı, ö, ş, ü' try this solution.
Go to start/control panel
Here, if you see Date, Time, Language, and Regional Options double click on it and continue with Add other languages. Select the Languages tab in the window that will show and click on the button that says Details... In the Settings tab of the window that comes now, click the button that says Add... In the drop-down box titled Input Language, select Turkish. In the drop-down box below that, named Keyboard layout/IME, select Turkish Q and click OK. Click OK until all the windows we opened are gone.
In the control panel, if you don't see Date, Time, Language, and Regional Options icon but there is an icon titled Regional and Language Options, double click that. Select the Languages tab in the window that will show and click on the button that says Details... In the Settings tab of the window that comes now, click the button that says Add... In the drop-down box titled Input Language, select Turkish. In the drop-down box below that, named Keyboard layout/IME, select Turkish Q and click OK. Click OK until all the windows we opened are gone.
Windows 98, and Windows Me Users
Go to Start/Settings/Control Panel/Keyboard
Click on the Language tab here, and then click the button Add.
Now, from the list of languages you see, select Turkish. Say OK until all the windows we opened are gone