Sorry, I meant to reply earlier.
Transferring cassettes to your computer for digital archiving involves several components. It may be possible to purchase a solution that combines these (for example, a tape deck with a USB interface and included computer software for editing your files) or you may be able to piece them together separately.
First, you need a playback unit. If you already have a good quality cassette player, or can borrow one, that takes care of that.
Second, you need a computer interface with DA converter to convert the analog sound output of the cassette player to digital files on the computer. Again, if you have a cassette player with a USB interface, that would include the first and second components.
Third, you need computer software to edit your files and possibly apply processing such as EQ, noise reduction and level adjustment. Audacity would be a very good place to start as it's free and fairly powerful. Though I have more advanced audio editing software for both Mac and PC, I find myself using Audacity at times for simple things like cutting off silence from the beginning and end of tracks, or taking a short section from a track (with a short fades at the beginning and end) to create sample clips. Audacity is straightforward and you shouldn't need any tricks or hacks to get it to do what you want.
If it were me, and I didn't already have a studio full of gear that would accomplish this, I'd try to do the conversion without purchasing a bunch of equipment I'll never use again. Assuming you already have a good cassette player or can borrow one, I would download Audacity (again, free) and then the only expenditure would be a low-end USB audio interface with analog inputs. You could get one of these for $50 or maybe even less by now. Install the drivers for this on your computer, play the tapes through the interface into your computer and record the result in Audacity. Edit as needed, save edited files in WAV, and burn audio CDRs for playback and data CDRs for backup, and you're all done for only $50 total expenditure. Using this setup, the only limiting factor in terms of sound quality will be the playback quality of the tape deck, so use the best one you can.