OK, this question comes up
all the time, "How do I share files between my Mac and PC". So, here is the answer. I'm hoping we can make this "Sticky" and save everyone time

I think I have remembered everything, if you think there is somthing I've missed then please post and let me know.
Networking Windows (2000/XP/2003*) with Mac OS X (10.3/10.4)
Information you will need to know
The IP Address of your PC (Start > Run > CMD {return} > ipconfig {return})
The IP Address of your Mac (Applications > Utilities > Terminal {Run app} > for ethernet connection ipconfig getifaddr en0 {return} or for wireless "ipconfig getifaddr en1" {return})
The workgroup the PC is in (Right click on My Computer, select Properties, and select the Computer Name tab)
System Configuration
It is important that the account you log in with on your XP system has a password set, if it does not you will not be able to login to your Windows share from OS X.
You need to put your Mac in the same workgroup as your Windows PC. To do this open Directory Access (Applications > Utilities > Directory Access). Click on the padlock in the bottom left corner to make changes; you will be prompted for your password. If SMB is not ticked off, then tick it off. Select SMB and hit the Configure
button. Now enter the name of your Windows workgroup. In my case the name is AD.
Setting up the PC to share files
You need to create and share a folder on your PC that you will then access from your Mac.
To do this create a folder (or select and existing one) right click on it from Windows Explorer and select Properties. Select the Sharing tab and share out the folder. Id recommend you use a one word name for the share. For example mac, not Apple Mac Share, it just narrows the risk of complications.
Setting up the Mac to share files
Open System Preferences (Applications > System Preferences). Go to Sharing under Internet & Network, and tick off Windows Sharing, and if it doesnt start by itself, click Start. This will share out your entire home folder.
If You're running Tiger (10.4), you will also need to click the "Accounts" button and tick off the box next to your account name so that OS X knows to share out your particular home folder.
Accessing your Mac from your PC
Click Start > Run and enter \\192.168.1.2\edesignuk, replacing the IP address with the IP address of your Mac, and edesignuk with the short user name of your account in OS X. When asked to authenticate enter your Mac accounts short user name and password. All being well you should now be able to see you entire home folder on your OS X system. You can also map this share like you would any other Windows network share so that it is accessible from a drive letter.
Accessing your PC from your Mac
To mount a Windows share on your Mac, click on your desktop so that Finder is the active application, from the Finder menu go to Go > Connect to Server. In the Server Address field enter smb://192.168.1.3/mac, replacing the IP address with the IP address of your PC, and mac with the name of the Windows share you created earlier.
When asked to authenticate enter the name of your PC in Workgroup/Domain (Unless your PC is part of a domain and your PC account is held on a domain controller, in which case enter the domain that you normally log on to Windows with). For Username and Password enter the username and password which you use to log on to your Windows machine with. Click ok and your shared folder should be mounted as a network drive on your desktop.
*Windows Server 2003 Authentication
By deafult Windows Server 2003 will try to encrypt everything sent to and from it. With this enabled you will not be able to log in to the share from your Mac.
To fix this there are a couple of options.
Case 1, your server is nothing more than a regular file server. In this case open up regedit (Start > Run > "regedit" {return}), and navigate to HKEY_LOCAL_MACHINE \ System \ CurrentControlSet \ Services \ LanManServer \ Parameter \ RequireSecuritySignature, and set it's value to "0".
Case 2, your server is also a Domain Controller. In which case you need to open the DC's Security Policy (Administrative Tools > Domain Controller Security Policy). Navigate to Local Policies > Secuiry Options, and disable "Microsoft network server: Digitally sign communications (always)" & "Microsoft network server: Digitally sign communications (if client agrees)". Reboot your sever, and you should be good to go.