The latest version of Trend has a couple of issues, namely it no longer supports Windows 2000 (This could be an issue if your site is still 2000 based) and the client agent does not upgrade properly on SBS 2003 servers.
After running the upgrade - the client agent is not installed properly and is not running on the server.
First make sure the latest critical patch is applied:
Next we need to remove all traces of the client agent from the server using the removal tool:
Now we should be able to install the latest client on the server without any further problems using the "\\Servername\ofcscan\autopcc.exe" method.
Source URL: http://community.trendmicro.com/t5/Business-Security-Forum/WFBS-7-0-installati-on-error-on-SBS-2003-servers/td-p/18164/page/6
Trend WFBS Download: http://downloadcenter.trendmicro.com/index.php?regs=AUS&clk=result_page&clkval=drop_list&catid=8&prodid=39