There have been a few posts regarding 2-way in-call recording in the Sony Experia X1 forum.

If you own a X1 and have tried to record calls on it, you’ll know that your Windows Mobile device records only your voice and the recipient/caller’s voice is heard with very bad quality.

XDA forum member ultrashot has posted a driver that fixes this problem and recommends a full backup before installing the driver.

You’ll need to install the NewSDKCerts.cab, then ultrashots’ driver cab file, and perform a soft reset.

Once installed, you’ll get a ‘Record’ menu item during calls and will also be able to use third party recorders.

For full instructions and to download the cab files, head on over to the forum thread.