Here's an easy way to hide your Windows PC on a network while maintaining access to network resources (this also works when you want stealth but still want to let others access your shared resources). Go to the command prompt (click the Start button, type in 'cmd' then right click on Command Prompt and select 'Run as administrator'). At the command prompt, type in the following line:
Net config server /hidden:yes
Now you're still a member of your network neighborhood but your PC won't show up when others browse for it. Make sure your software firewall is turned on, and block incoming ICMP traffic. This will prevent a network intruder from scanning for your PC using a ping sweep.
If you want to get rid of this measure, use the exact same command, but instead of yes at the end of the command, put no to turn it off.