I have 1500 cds

You will need about 600 Gigabytes if you store them lossless.

what is lossless?

I am no expert in and haven't done it myself so I hope others chime in.
It's file type in this case it is considered one of the more exact,well,a virtually exact copy of the digital data it is given. CD-W is simply a ripped copy I was thinking of records when I read this.
I have heard that a WAV file is one of the better files if not the best. Lossless I think was initially for Apple computers, i-pods etc, but now available for other platforms .ie. Windows

Lossless = Apple Lossless and FLAC (free lossless audio codec). They both maintain 100% of the information whereas mp3s and AAC files trim data to make the files smaller. Apple lossless and FLAC store the data in a compressed format and the software uncompresses it as it is played.

WAV and AIFF files are uncompressed Lossless files. Many people, including me, find that they sound better than apple lossless and flac. They also take about 2-3x the space, so usually about 50-60mb per song. I'd get 2 terabytes and rip them in AIFF.