Hi Douglas,
Ferd II's link is excellent if you have a router, but it can be done without one. Though you do need a cross-over Ethernet cable. That's why the Mac and PC can't see each other with a standard cable. Then follow these instructions.
1) Open "My Network Places" on the Windows computer.
2) Double click on "Add a network place".
3) A setup wizard will appear. Click next and choose the option to specify a network site, etc. Click Next.
4) Open the System Preferences on your Mac. Choose Sharing. Under the Services tab, turn on the check box for "Windows Sharing". Click on the Accounts button and activate your account. If sharing hasn't started by itself, click the Start button. Write down the address where it says "Windows users can access your computer at...". It would be something like
\\192.168.0.122\username
5) Enter that address in the wizard at the Windows computer and click Next.
6) It will take a few minutes for the connection to show up. When it does, give the connection a name and save it.
In the future, you then just need to have Windows sharing on at your Mac and double click the connection you saved to connect. When you do, a dialogue box will appear asking for the Mac users' name and password to connect. Put in your long name (the same one that appears any time the Mac asks for your password) and the password. A folder will open on the Windows desktop.
Initially, it will only let you set the connection up for your entire Mac account. So you will see all of the folders within that account. If you want to confine the connection to the drop box, then run the connection wizard again. This time, on the page where you enter the Mac address, you'll have a drop down menu of all of the folders in your account. Choose
username\Public\Drop Box and save that connection. Delete the previous one. Now when you connect (using the same long name and password), the folder on the Windows desktop will be confined to the Drop Box folder of your account.