I would recommend you consider buying hardware based router / firewall. Linksys make some very nice gear and it’s not that costly.
One thing to be carefully about is look at the features like firewall control.
Belkin for example are designed for basic home users and that makes it hard if you want to setup a few custom firewall rules. I’ve also had trouble with Belkins not passing IPSec traffic from my VPN client. The Linksys just works.
I use a WRV 200 Linksys it supports VPN access to my network has DYN DNS polling plus supports wireless. They did cost about $120.00 but they have been superseded by the N series so they may be cheaper now.
A stock router / firewall with no wireless would be around $50.00 - $70.00 and would not use the power nor generate the noise from a PC based unit.
If you really want to have a second PC running to act as a router Linux and Squid or for a Windows based system have a look at this link - its free too>
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