mmmm, Size DOES matter, because when you convert the audio to 44.1khz, 16-bit (for an audio CD), size is directly proportional to the length of the song (to the tune of approx. 10MB a minute). SO... if you have a 5 minute song to burn to a CD which takes up 1GB on your HDD, something is very wrong!
Also, someone mentioned on here that CDs contain .cd files, and not wave files, that's not really the case. The audio data (the actual bits) on a CD is EXACTLY the same as wav data. The headers might be a different (as well as the audio CD having a TOC) though. There aren't actual .cda files on your CD. When Windows sees an audio CD, it looks to the TOC, and makes it appear that there's a file for each track (in .cda format), but that's not really the case. If it was, you could just copy that .cda file to your HD, and have the track exist there. But the cda file is really just a pointer to the wav data (notice how small each cda file is?) So when you rip a CD to your HD, you're not really converting the data, just the format of the data (from the format on a red-book CD to a Windows .wav file)