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Jade: Nice. =P
Basically, what I meant, was that Portal and TF2 share the Source game engine, what makes it run. Theoretically, if Portal's installed, then you could then install TF2 quicker; however, since TF2 has thousands of different items, it might not be as large a difference compared to if it was Portal being installed quicker, since there would be more unique objects.
And the second question was about what internet settings you have set, like what it asked you when you first set up Steam. =) It shouldn't really do anything(And if you keep getting that problem, it might be your internet, period, for some reason...), but changing it to something higher might help.
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That would be correct. Both Portal and TF2 use the Orange Box (AKA 2007) version of the Source Engine. As a result, if you already have one installed the other will install more quickly, because it mostly needs to just download models, maps, animations, sound files, etc. since the engine files are already there.
If you already have an Orange Box-version Source game installed when you try to download TF2, you'll notice that the download progress will skip to about 65% or so, and then progress at a normal rate. This is why.
Jade: May want to uninstall and start over if it isn't booting.