1.
What level of "Vista Home premium"; e.g. RTM, SP1?
2.
Security Software. What security software are they running on that "Vista" box. You might want to "disable" it (or uninstall it, but only if you can reinstall it again). May be able to use "msconfig" from Vista to do this.
3.
Network Connections. If you're going to troubleshoot on your network with your ISP (which may require different interface than theirs), I'd uninstall, disable, and remove their network configuration including "defined" network connections (and possibly network adaptors) and redo it fresh for your test environment. (No, I'm not suggesting a restore/recovery of their operating system - not yet, at any rate).
a. Don't reinstall their "wireless" network adaptor if you're testing with "
wired" adaptor. Keep the problem domain small.
b. Disable startup of "belkin wireless network utility". Think you may do this in Vista from "msconfig" utility.
4.
Home Router. Connect "visiting" computer to home router, that way you may configure it to connect same way as any other "Vista" home computer you may have. Also gives web interface (home router web configuration interface) on local area network to "ping" or connect to using "http" protocol; e.g. "http//192.168.1.1" or whatever IP address you've configured your home router to use.
5.
Software Firewall. I'd disable any software firewalls they might have running while you're troubleshooting network connections. If they are behind your "home router" which has "firmware" firewall, it should be safe. If this concerns you, disconnect router from modem while testing your LAN connections.
6.
Use "ping" from "visiting" computer through home router to Internet. Record the results:
a. ping 127.0.0.1 ; Test IPv4 TCP/IP protocol stack.
b. ping <visiting_computer_ip_address> ; even if it's in APIPA range "169.254.x.x".
c. ping <home_router_ip_address> ; should be your "default gateway" address.
d. ping <another_LAN_computer>
e. ping <69.72.169.241> ; computerhope website
f. ping <
www.computerhope.com> ; computerhope website
7. Some links for information only. I don't have experience with "Vista", so I'm trying to get a handle on the "networking" changes.
a.
Resolution of Vista Unidentified Network or Limited Connectivity b.
Vista Issues c.
Vista How to d.
Unidentified Network Issue In Microsoft Windows Vista or "Local Only"