Incidently, the last menu option in the omake (where the CG list, etc lives) lets you change your Windows system sounds to sound bites from the various girls. They mostly seem to be custom made especially for windows, not just ripped from the game. (For example Ohayou, Sensei (Hello Sensei) for startup, and Atarashii Me-ru (New mail) for the new mail notification.) Looks like you can select any of the 5 girls, and what they say varies on their character. (In decreasing order of familiarity: The purple haired girl just says Ohayou, the little blue haired girl says Ohayou, sensei. The other three all say "Ohayou gozaimasu, sensei", but with different inflections according to their personality. (Blondie is too cheerful - Ugh. The green girl sound more demure than angry - not too sure what's up with that)
The background music is available as MP3s in the game's install directory - at least in a full install.
The wav files for the system sounds are in the Omake directory on the "CD"