can't record any sound from Realtek sound card (Windows Vista, Sony Vaio laptop)

Try to install the latest Realtek HD Audio driver for your laptop that Sony offers.

Make sure your laptop has Realtek HD Audio:

1. Right-click on the speaker icon in the system tray
2. Click "Playback Devices"
3. Double-click "Speakers"
4. On the "Controller Information" section, click "Properties"
5. Select the "Details" tab
6. Choose the "Hardware Ids" property
7. Verify that the "PnP ID" looks like "HDAUDIO\...VEN_10EC". If it is so, then you have a Realtek HD Audio card.

Realtek High Definition Audio Driver download and installation instructions from Sony:

1. To ensure that no other program interferes with the installation, save all work and close all other programs. The Taskbar should be clear of applications before proceeding.
2. Download the REDAUD-12655000-US.EXE file to a temporary or download directory (please note this directory for reference).
3. Go to the directory where the file was downloaded and double-click the REDAUD-12655000-US.EXE file to begin the installation.
4. At the "Realtek High Definition Audio Setup Program" screen, click "Next".
5. At the "License Agreement" dialog, read the agreement, then, if you agree, click "I Agree" to continue with the installation.
6. At the "Finish" screen, click "Finish".
7. The installation of the Realtek High Definition Audio Driver is complete.

Originally Posted by any ANONYMOUS forum user

I have onboard sound and Camtasia was not recording it.

If you can't get the Stereo mix option, you can still record audio from your sound card and video from your screen using software that uses Universal Audio Driver.