Conversation so far:
Did U and  Don't Don by Super Junior have success?
Super Junior's U exceeded 400,000 downloads within five hours of release. Don't Don became the second best-selling record of 2007.
DidSuper Junior go on any tours during 2006–2007 with U and  Don't Don?
Are there any other interesting aspects about this Super Junior article besides that U exceeded 400,000 downloads within five hours of release and ultimately surpassed 1.7 million downloads, crashing the server?
In late 2006, Kyuhyun, Ryeowook, and Yesung formed the subgroup Super Junior-K.R.Y., Super Junior's first sub-unit.
Was subgroup Super Junior-K.R.Y., Super Junior's first sub-unit also successful?
Super Junior-K.R.Y. performed their first single The One I Love, theme song to the Korean television drama Hyena, on the KBS music program Music Bank on November 5, 2006.

Question: How many copies or downloads were sold ?
Self-contained rewrite: How many copies or downloads were sold of U by Super Junior?