To be able to run Android 2.1 on your Dext you need an updated radio.
Check your baseband version in the phone settings: If you still have a *5012* baseband radio you need to upgrade at least to 5025.
Use the following instrucctions, depending of your carriers 3G/WCDMA base bands (you can check on your Dext box). Don't mess up, or you will loose 3g access for ever.
Please note that what matters here are the 3G/WCDMA frequencies, not GSM one.
Flash that 5025 radio using custom recovery: radio1318only-signed.zip
Flash the 5025 italian radio using RSD Lite. See Italy 3025 Radio at M3.Obvious: If your baseband version is already 5025 or superior, don't use that instructions at all.