Default to Home Network if no Internet Access?

[babcom]

Hi there,
I have two PC's, call them PC A and PC B. Both run Windows 7. PC A is a newer PC with a decent gfx card attached to a nice LCD monitor. PC B is older with a not-so-good gfx card attached to a not-so-good CRT monitor. I want to watch movies stored on PC B on PC A and have internet access on PC A at the same time. I do not need internet access on PC B. So I bought a switch, knowing that your ISP only allows one IP address, but this was okay as I only want to use PC A for internet access.

Problem: Having set up the homegroup, if I start PC A first, I get internet access on a home network. I then start PC B and because it has no IP address and has no internet access, it defaults to a public network. I can't see PC B on the network (I assume because they are different networks but see below when I turn on PC B first).
If I turn on PC B first then turn on PC A after PC B has got internet access, B is the home network and A is the public network but in this scenario I can see B from A but I do not want to use PC B for internet access.
I can use the windows troubleshooter and it will change the public network to a home network but this is too much trouble. I do not want to move the movies to PC A.

Question: is there something you can change on PC B so that if it does not find the internet, it will default to a home network?
If not, will buying a router solve my problem?

 

[NesuD]

Get a router and Both PCs will be on the same Class C private subnet which will allow them to communicate and make internet access available via NATto both of them while only using 1 public IP. The way you are trying to do it won't work.

 

[babcom]

I have gotten this to work using the switch. I discovered that if you manually assign a fixed local IP to PC B (using the cable modem's IP), both PC's will boot up as home networks which is what I needed