I would save my slef the headache and get G-Alarm. I am not sure why MS/HTC can't put a usable alarm clock on the phones.
http://www.ageye.de/index.php?s=galarm/about
I know if you search hard enough there is a free version floating around too. i think V1.5 is free to use and newer versions cost about $7 U.S. but well worth it