On the startup options screen try "Last known good configuration" . If you are able to boot into Windows download and run the Norton removal tool -
http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039 It is likely your Norton product did not uninstall correctly and this conflict with One Care is causing the stop error. If this does not resolve the issue or if you are unable to start Windows send an e-mail with One Care in the subject line to
jrap107@msn.com and I will help you reach support.
Jim - MVP Windows Live - Forum Moderator - Live One Care - Live Mesh