Well, the answer depends on what you intend to do with the files. First of all, you should rip (take songs from a cd, and add to your computer's HDD) everything @ 128kbps. This will give a high quality sound, without taking up too much space on your hard drive. You can encode at higher bit rates if you want to, the higher BR, the better it will sound. Don't encode at anything lower than 128, as you will start to notice a deterioration in the sound at the lower levels. Now, the file format depends on how you will be using these files. If you have an MP3 player other than an Ipod, then you can either encode in MP3 or WMA, with MP3 probably being the better format, as they will play on most any player, while WMA (Windows Media) files will not play on the Ipod. Ipod actually uses a proprietary file format (ACC), but will also play MP3. Things are further complicated by the fact that any music you download (and pay for) will be protected. What this means is, if you were to download a song from Napster, it would be a protected WMA file, which means that your use of that file would be restricted. A protected WMA file cannot be converted to an MP3 file, unlike a an unprotected WMA file (such as one you ripped from a CD of your own) which CAN be converted. The protected files will only play on players that allow the WMA format (read: not the Ipod). Likewise, if you were to purchase a song from the Itunes music store, it would be a protected ACC file, which could not be converted either. I guess the bottom line is, encode all your CDs in the MP3 format @ 128 kbps, just in case you ever buy an Ipod... converting all of them from WMA is a slloooow process!

The best format for archival purposes is one that retains as much of the original signal as possible without producing irreversible changes, such as occurs with lossy compression. Ideally, one would use 24-bit, 96 kHz to archive original music. However, it the music has already been formatted for CD, the best you can do is 16-bit, 44.1 kHz. Lossy compression works by tossing out data - the higher the compression rate, the more data is discarded. Once compressed with a lossy algorithm, the original cannot be recovered. Any resulting reduction in sound quality is permanent - it cannot be corrected. High resolution audio can always be compressed for archival purposes using a lossless compression format, such as zip.