Sharing files with Windows users

I have a PC (Windows XP Professional) and a Mac Book Pro (Mac OS X ver. 10.5.8).

I am trying to share folders / files between them through my network's modem-router. I managed pretty fast to make PC folders to be viewed by the Mac but the other way around doesn't seem to work: Anything in the Mac is invisible to my PC!!!
When I go in Windows Explorer to "My Network Places / Entire Network / Microsoft Windows Network / Workgroup" and I click on the name of my Mac I get a message saying "Mac is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. The network path was not found."

Previously I did follow the set up procedures found in Mac Help at "Setting up a Mac computer to share files with Windows users."

The problem is that in these instructions it says: "Give the address of your computer (Mac) to Windows users you want to share your computer". But what do I have to do in my PC with the Mac IP address? Where should I input it under Windows?
Thanks for helping, because I had spent more than one hour over the phone with an Apple technician and he couldn't figure it out!!!

If you are sharing your files through SMB (Sharing Preferences > File Sharing > Options > check "Share files and folders using SMB (Windows)"), go to Start > Run and type in "\\<ip address>" (w/o the quotes). Replace <ip address> with the IP address of your Mac.

also, make sure the firewall allows access.

How?

Thanks for replying.

I tried to type in Windows, at Start - Run: \\<ip address> but it does not run. It says "\\ip the network path not found" or "Windows cannot find ip. Make sure you typed the name correctly ..."

What to do?

Again, thank you.

you need to put the ip address of your mac.. or.. something like

\\192.168.0.1

to get this look in your network preferences..

you should see something that says something similar to...

AirPort is connected to xxx and has the IP address 192.168.7.21.

""you need to put the ip address of your mac.. or.. something like

\\192.168.0.1""

I already know the Mac's IP address.

The problem is WHERE in my PC's Windows do I have to input this address?

Where exactly do I have to go in the PC and actually type the Mac's IP address? This is what the Apple technician didn't know either.

Thank you!!!!!!!