Open up the mixer control panel for your sound card by double-clicking the little speaker icon in the lower right corner of the screen. Click Options / Properties / Recording / OK. You will now be looking at the recording inputs. Select the one that has a name something like "Mixed Output", "PC Speaker", or "What U Hear". When this is selected Vegas or Sound Forge (or any other audio program) will be able to record anything you can hear from the computer speakers.