Carol, going from the beginning, you have to understand what the process is. If you know, disregard this post.
To get the sound (streaming audio) onto a computer, it must be digitised into a format the computer can use. WAV files is the Windows standard, there are several more. You will be familiar with MP3, which compacts the music for use on portable players, losing a little in the process. Most people record in WAV. The simplest digitising program I've found (there are few options in it!) for this is called LP Recorder and earlier versions can be found on coverdisks.
You must connect the tapedeck into the sound card of your computer at Line-In, next to the earphone jack.
Sometimes a computer won't accept input, usually because it isn't selected. If you have this problem, go to Control Panel and select Classic View (I hope Vista is the same as my XP) and search until you find something 'audio' deselected.
Then play around with the speakers switched on until you work it out.
Start with the volume on the tapedeck turned low until you get it working well. If the sound comes out of the computer speakers, then it is going into the computer! All you have to do is digitise and then store it.
I'm using a tapedeck from a midi system connected from the RCA audio connections on the back.
Theoretically, you should have a 'preamp' in the tapedeck. I have no idea if I have, but it works for me, and I hope it works for you.