If you go to the command line and type ipconfig /all
what do you get? if you get an ip address can you ping the ip address of the router?
In network properties do you have "file and printer sharing enabled"?
Do you have "client for Microsoft networks enabled"?
Are the two machines in the same workgroup?
Do you have any security settings in place on router?
Do you have a software firewall installed?
With your wireless, do you have a good signal strength?
Are those files in a folder that has been shared?
Just some of the stuff you might want to take a look at. The more info you post the better!
Jnbh