Well, look at Windows 2000 or XP. It comes on one disk with other information and files on the disk, but after install Windows is about 2GB. All from a single CD at about 450MB.
Some files have the ability to compress a lot more then others. Music and graphics are two files that don't really have room for compression.
Soyo Dragon Ultra Platinum Edition powered by a P4 3.06GHz w/HT @ 533FSB
ATI Radeon X800Pro 256DDR <---Yeah!!! I finally got it!!!
1024MB PC3200, Creative Audigy LS, 2 x 40GB = 80GB RAID 0
Windows XP Pro, DOOM 3, CS, UT2004, BF1942 RtoR, CNC Generals
Finished Half-Life 2!!!!!!!!!!