IMHO you don't need to buy a sound card. AFAIK most integrated sound cards can play sound and record it at the same time.

It seems that you tried to use Windows software that doesn't work on Vista. You can record from your sound card on Windows Vista with the following software: freeware Freecorder Toolbar, freeware Jaksta Free Media Recorder, shareware Replay AV and Replay Music and some others.

Freeware Freecorder Toolbar and Jaksta Free Media Recorder work with ANY sound card, even those that don't support recording (like RealTek and SigmaTel). They work on Windows Vista and Windows 7.

Please note that Windows Media Player 11 on Windows Vista may use a "protected audio path" technology which prevents recording. So you won't be able to record protected audio content on Windows Vista. It will work fine on Windows XP though.