WTH didn't you say that in your original post...lol.
I've never heard of somebody using the tape-to-cdplayer adapter to connect to their laptop. Do you if the cord will fit into the soundcard or not?
Anyway, 50 bucks man...tape player is easy to get nowadays. Ebay may be your best bet...guessing $20. Just make sure it's from someone reputable (you know that) and works

. I'm sure ebay is saturated with older tape players people dont' want anymore.
This is fuggin complicated, man.
Just get an mp3 player for your car.
Warthog