External Hard Drive Networking Issue

I'm using an iMac running Lion and a PC running Windows 7 and I'd like to share an external Seagate hard drive (FAT32) over my local network. I've turned on File Sharing and enabled the drive in question; the drive is automatically set to give read/write access to "Everyone." However, while the PC detects the drive on the network, it will not allow me to connect to it, and gives me the following error:

"[drive] is not accessible. You might not have permission to use this network resource. Contatct the administrator of this server to find out if you have access permissions.

"The parameter is incorrect."​

I am able to access other shared folders on my internal HD without difficulty.

The only thing I can think that might be causing this is that I had to create a user account on my Mac that matched the PC's user name and login; this account does not appear in the "Users" window in the file sharing settings, and the system won't let me add it (or any other account).

I'm not certain how to proceed. I'm not opposed to reformatting the external HD if necessary, but I'd like to avoid it. And because the iMac is my primary computer, for speed reasons I'd like to keep the external HD connected to the iMac and access it from the PC over the network when needed.

Thoughts? Suggestions?

 

Yes, I enabled SMB sharing; for whatever reasons, the user accounts I enabled in SMB sharing do not appear under "Users" when the external HD is selected - I only have the primary user for the iMac and "Everyone."

 

Sadly, no. I eventually decided to move the folder I wanted to share to my local hard drive and use the external for backup.