Trend Micro has a support page that helps with removal instructions:
http://esupport.trendmicro.com/support/consumer/answerguide.do?RF_command=createNewRFIncident&RFID=RF_CON_TS_UNINSTALLATION_1_1
If that doesn't help, please contact OneCare support:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve