Copy all the songs you wish to include in your mixtape to a separate sub-folder within your "Music" folder. Right click on the track name and choose "Copy." Right-click and choose "Paste" when you have navigated to your new folder. Label the folder "Mixtape."
Open Audacity and load up the track you want to put first on your mixtape. Load a track by clicking on "File" in the top-left corner and selecting "Open." Alternatively, press "Ctrl + O" on your keyboard. Browse to your desired audio file. Audacity will import the file and display it as a waveform.
Locate your second track in your "Mixtape" folder (go to your "Music" folder under "Libraries" in Windows 7). Click and drag the file into Audacity. It will appear underneath the first track.
Click on the "Time Shift Tool" in Audacity. The two tracks will play simultaneously if you don't move the new one. The "Time Shift Tool" icon is a horizontal line with two arrow-heads pointing away from each other. Click the bottom track and drag it to the right, so that the waveform starts when the previous one ends. Most tracks will have a quiet portion at the beginning and end, which can be overlapped for a smoother transition.
Repeat the previous two steps for each track you want to include in your mixtape. When you are done, click "Tracks" and choose "Mix and Render" from the drop-down box. Audacity will then mix your tracks. Click "File," "Export" to save your mixtape track on your computer. Select "MP3" from the "Save as Type" drop-down box if you wish. Name your mixtape as desired and advance through the screens. Audacity will bring up the "Locate Lame" pop-up box. Click "Download" to install the add-on and save the track as an MP3.
Connect the 3.5 mm stereo end of the audio cable to the "Headphone" jack on your computer. Connect the red and white composite cables to the "Input" on your tape deck. Insert a blank tape. Press "Record + Play." Play the mixtape track on your PC to record it to the tape. Alternatively, burn the MP3 track onto a blank CD.