I have to admit, I've been using endpoint for a bit, but I always like to have as many layers as possible- starting at the modem :)
I don't know what resources you have available, but have you considered setting up a domain controller?
OP- Are you the only user on your LAN?
Funny story- I was at the Microsoft release of Office 2007 when one of their demonstrators was showing off the capabilities of some...
Anything within the range of 224.0.0.0 - 239.255.255.255 is reserved for multicast use, and is most likely coming from your router or another host...
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