Approx. how many CD's on 4 gigs?

Well, let's do the math. Say your average CD is lucky enough to run 50 minutes or 3000 seconds, that's 3000 x 192k = 576,000,000 bits per CD. Divide by 8 for bytes = 72MB per CD. 4000/72 = 55.5 CDs on the Nano. Figured another way if there are 12 songs per CD (12 x 4 minutes per song = 48, pretty close to the theory 50) = 667 songs, which is reasonable as Apple says 1000 will fit at 128kbps.

So between 50 and 60, hey?

Apple says it hold about 1000 songs at 128 kbps, so it'd hold about 667 songs at 192 kbps. (1000*128/192)

Another metric is: at 128kbps bit rate, I consistently loaded approximately 68 hours of music on my mini (with a true available storage fill-rate of 3.7GB for the 4GB mini or nano).

So figure on around 45 hours of music at 192kbps.

It will depend on the actual run time of your CDs, of course, but expect 45-55 reasonable sized CDs. Less if they are extended or double, more if they are shorter.

currently i have 692 songs on it and a bunch of contacts (don't know how to get a count of them apart from manually counting) and its taking up 3.7 gigs