Alternate data streams http://searchsecurity.techtarget.com/definition/alternate-data-stream
Browser helper objects http://www.sysinfo.org/bhoinfo.html
On balance I would still recommend Avast purely from my own experiences but, I have never used a Raid system 
Windows 7 once you get use to it is a superior OS to XP in many ways as the security is a lot tighter. Plus XP will no longer be supported next year so it will be the target of choice for malware writers
How is the computer behaving now ?