I suspect the problem arose because Norton wasn't uninstalled before Trend
was installed. I would suggest going to Add/Remove Programs in Control Panel,
and make sure that BOTH are fully removed, restart the computer, then try
installing Trend again.
If you still can't get rid of remnants of Norton, there is a remover-tool on
the Symantec site.
There is also a possibility that a broken Layered Service Provider is the
cause. A program called LSPFix can be found on various sites which will fix
this.
http://www.cexx.org/lspfix.htm
DO use with caution as it's possible to do further damage if you don't read
the instructions!