[Fyron]

The most important thing to check in Vista is whether or not the network is considered private or public. When a new wireless network is joined for the first time, the system asks you whether it is a home, office, or public network. The answer sets network access privileges for a slew of services. You can check these settings in the Network and Sharing Center (Control Panel > View network status and tasks). Network Discovery and File Sharing are necessary services to be able to share files. You should make sure these things are enabled before fiddling with IP addresses.

Another thing to check is that all machines are in the same Workgroup. Different Workgroups will also prevent network discovery from being successful. You can check and change Workgroups in the System Properties dialog (accessible in Vista via Control Panel > System and Maintenance > System).

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Regarding setting a static IP in Vista:

Typing the full command.com in run dialog is unnecessary, as "cmd" maps to the command line prompt.

Vista method:
Open Explorer.
Right click on Network in the left-hand tree view, select Properties. (Alternatively, you can get here via the Control Panel, by clicking on "View network status and tasks" below "Network and Internet.")
Click on "Manage network connections" on the left.
Right click on "Local Area Connection," select Properties.
Now follow Jack's procedure above, starting at TCP/IP properties. Make sure to select IPv4.
Select TCP/IPv4 on the list
Click Properties
Move from "Obtain an IP address automatically" to "Use the following IP address."
Put in the numbers appropriate to your network (the IP address itself needs to be unique, but you can clone the rest off of another machine on the network - open up the command prompt (start, type cmd, hit enter) and type in ipconfig - that should get you most of it)).
Hit Ok/close out of everything.

Note that Vista should automatically refresh the IP after confirming the changes, so the ipconfig step is generally unnecessary. If you end up needing to refresh it, you must run cmd in elevated privilege mode. Hit win-key to pop up the start menu, then type cmd. "cmd.exe" will appear in the results. Right click on it and select "Run as administrator."

I should also point out that rebooting is generally unnecessary to change IP address in Vista, XP, and even Win2k. Most of the time, they handle everything just fine.