when we say "dedicated machine" it typically means a system designated for a single purpose.
The poster above sounds like he's only got one computer and uses it to skype and play facebook games while he's working.
If you use your old pc to go online, chat, and whatever, and you truly dedicate a machine for modelling, you don't need half those specs.
most of you programs cant even use more than one core, and a couple GB of ram.
the biggest advantage of having an offline machine (not connected to the internet) is you don't need the biggest resource hog ever, anti-virus software. without anti-virus software, any system runs twice as fast. test things with your regular pc before moving it to the offline system if you're worried about viruses.
no skype or other ridiculous video intensive programs running in the background, no steam, no advertising overflows from facebook, everything unnecessary removed and or disabled... you'll be able to do 3 times as much with half the machine.
truly dedicate the machine to what it's dedicated to