I have a cable that fits into the tape deck & other end fits into microphone socket. Do I have to download any software to enable me to record?

It won't be top quality or anything but it is doable. You will need a program to handle it. There's a free program called Mp3MyMp3 that works great for this. Just set it to your input (microphone jack) and if you want it saved as a wav or an mp3. Wavs have better sound but they're a LOT larger files than mp3s