Does your computer have sound capabilities? Can you play audio files on your computer? Your PC/Mac audio output can probably be sent as input to your analog lab. Just cable the sound card "line output" to the lab console audio inputs. Sony LLC-9000 users can find the "front" inputs on the console lower front panel, under the "desk" area. Move your chair out of the way and sit on the floor, they are right in front of you. For details on making the connection, read Connecting Your PC to Your Stereo from the magazine of the Melbourne PC User Group or Connecting Your PC to Your Stereo from The MP3 and Internet Audio Handbook by Bruce Fries. Substitute "Analog Language Lab" for "Stereo".
If your computer has sound hardware but you don't have an MP3 player, visit the MP3 Software Players page at MP3.COM. They have links to MP3 players for nearly every computer platform.
Read Sound Digitizing Process from CHILDES at Carnegie Mellon to learn how to digitize your existing analog (usually tape) recordings.
Of course, you can use the computer's microphone and sound recording application to make your own original digital recordings. Read Digital Sound Recording for an introduction with Windows based examples. Randall's ESL Cyber Listening Lab has a tutorial about making digital sound and vdieo files for web pages. If you ignore the "web pages" bit, everything else applies.
Griffin Technology, Inc. makes the iMic, which permits audio in connections via USB ports on Macs and some PCs.
To display the entire computer screen, you need a scan converter or a video card with a "TV Out" port.
A scan converter sits between your computer and your monitor. The scan converter output is cabled to the console "front" video input (an RCA jack).
If your video card has "TV" output, it might be "s-video" or "RCA". S-video outputs can be connected to RCA composite inputs with a simple adapter.