You can. There are a few ways this can be accomplished.
One way would be to connect the line out from the tascam to the line in on your soundcard. Depending on your budget, you can purchase a nice soundcard and the editing software to really make a nice mix
or you could just use what you got. Really depends on your vision of the end product...
There are a plethora of resources available on this bbs to determine what you need, if so desired.
Anyways, you could connect the tascam to the pc and send one track at a time to the computer where you could put them all together later.
Or, you could go with the easier method of mixing down from the tascam to a cassette. Connect a cassette player to the line in jack of the soundcard (using a 1/8"M to 1/8"M will do the trick for a basic set up...found at radio shack for a couple dollars). You can use any type of wav editor software, such as creative labs wave studio - quite lo-fi. Keep in mind you aren't going to get the best sound quality here...but it will work.
I used this method for a while to listen to quick demos in the car. It helped me think of parts to add while driving to work. Worked well until I hooked up a makeshift studio in the car - went way overboard...that's another story though...
