This is very strange, indeed. "inetmgr" is the internal shortcut for IIS Manager (actually, the name of the executable, as opposed to "appwiz.cpl" which requires rundll to work). Not finding it could mean that you haven't installed IIS at all.
Installing IIS under Vista Home Premium is described here
If for some reason the search (run) box does not work, you can
alternatively start IIS Manager via Control Panel->Administrative
tools->Internet Information Services (IIS) Manager. Then follow the
exact same steps.
Without IIS, you will probably need some luck with apache
+ sitefinity compiled for .net 2.0
. This is not supported, but with some luck it might just work.
I hope this will help you. If you need further assistance, contact us.
the Telerik team