The built-in ringtone library only supports files up to 300 kb, (though I couldn't set the 297kb umyaya.ogg for St. Olaf College either...). The work-around is to install Rings Extended app (free) from the Android Market, then:
Home->Sound & Display->Phone ringtone->Music
Choose your favorite piece, and click OK to save.
Picked up this little nugget from Forged Defiance:
With a little side of applesauce...
©2006 Shannon Eric Peevey