I need to install/import a CA cert (.cer) into the Trusted Root Cert Authorities store of a Win XP Home using command line. Anyone has any idea which command i can use?
Certutil.exe should do the trick, more details here in this Microsoft KB article. I've only used certutil on Server 2003 and XP Pro but according to this Microsoft KB XP Home is not listed so you may have issues.
If Certutil doesn't work for you you may be able to use a third party tool. Here's an example of a project that appears to do this but if there are issues with Certutil working I suspect there may be issues with this too, although you might be lucky.