How to completely uninstall SQL 2005 Std on Vista?

I have just migrated from XP Professional to Windows Vista Home Premium using Laplink’s PCMover. PCMover gives no choice but moving everything to the new PC. I tried to uninstall everything related to SQL 2005, but whenever I try to install SQL 2005 Standard’s database engine or analysis service, I get an error saying there is already an instance.

I tried the following command:

"%ProgramFiles%\Microsoft SQL Server\90\Setup Bootstrap\ARPWrapper.exe /Remove

I also tried:

start /wait msiexec /x {GUID} /l*v c:\sql_uninstall.log

Is there anyway to completely uninstall everything of SQL 2005 in my situation?

Thanks in advance!Problem solved with the help from another thread:
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1964147&SiteID=1&mode=1

I also diabled firewall to address the error message about "transaction manager is not available".