Win 7 lost the connection to my homenet after plug was changed

This is a strange problem for me.

I had hand wired an rj45 ethernet jack on one end of an ethernet cable with the plug still good on the other end.

I then plugged my working ethernet cable to the jack end and the plug end to the motherboard NIC connection.

The result is I lost my homenet setup with a second machine in another room. This is just a two station
homenet connected to an XP machine and does not use the Win7 standard homegroup but the _workgroup_ convention.

Connection to the internet is working and I am using that now.

I checked and rechecked the wiring of that ethernet jack and simply ran this as a test
to see if the jack was put together properly.

How can I get my other connection back? No restore point was set and I'm not sure if that is even the answer.

Please give the steps for Win7 to discover my other homenet computer.

In the meantime, I am going to try to load a backup clone disk and see if that retained the
settings.

An update to save some grief.

This might have been a wire giggling solution.

I tried my backup disk and that failed too.

Then I started checking the cable run itself and put the original HD back on.

My second PC now shows up as it used to.

The question is, how did the connection get lost? Which element of the cable just communicates the
workgroup but continues to run the internet?

My architecture is

PC 1 Ethernet to 4 port switch box to DSL modem
PC 2 same

For now I'm leaving the thread open in case of a future error. Will report back.

This question also occurred to me:

In a standard RJ45 punch down jack, how many lines are actually used or are all handling data?

If I want to test my cable with the RJ45 jack one end and ethernet plug the other, would disconnecting
a particular pin prevent problems? Simply put, are all lines used or some 'in reserve' for future application?