Wired & wireless trouble

Hi, I have PC-A (Vista) wired to modem/wireless-router, PC-B(Windows 7 Pro) wireless connection via USB adapter, and PC-C(Windows 7 Pro) that I want to wire thru ethernet.

Internet access OK on A & B, not required on C. I Just want to share files between B & C.

1st question: Do I need a crossover wire between B and C?

2nd question: PC-B already has a homegroup with internet access. When I tried to join that homegroup with PC-C, I lost Internet access on B and got multiple network, could not join. I had to restart both PCs to regain access. What did I do wrong?

In short, I just want to share files between PC-B & PC-C via ethernet, internet access not required. I visited a dozen links on your forums but could not find a solution.

Please help!!

Thank you for the quick reply

PC-b and PC-C are side-by-side so wired connection seemed like a good idea, but the router is another room too far for wired. So you say I should get another wireless adapter for C, but like I said, I don`t really want internet on C, it`s a music workstation, so no antivirus, no browser, no clutter. But all my programs and downloads are on B and I`m tired of transfering stuff by dvds and usb

Could a wireless connection put the workstation more at risk?

Thanks

Oh yes, all pcs are on same workgroup

Add another nic to comp B, use cable to connect through those adapters... OR just connect via router and remove internet access through firewall/secpol.

I don`t use the inboard nic on comp B since it`s wireless, but when I tried to connect it to C, I ended up with multiple networks on B and lost the internet. Also could not create a homegroup on B and C that could see each other. Never mind A, I don`t want access to that one. Seems to me that the problem is with B. How can I create a separate network just for B & C that won`t conflict with the wireless connection between A & B?

Update!

Connecting B & C via ethernet, I can see and share folders between both comps. But still, I can`t join a homegroup for some reason. Isn`t it better to share via a homegroup, more secure? I had to share folders to "everyone". Does that mean that comp A with router can see everything, therefore internet also?

mmmh, not sure

homegroup is "meh" at best - If it works... just let it work.