computer or sharename could not be found

I'm using Windows 98se on 2 pc's connected via RJ45 to a Siemens router with a Linksys Cable Modem. Both pc's have no problem accessing the internet, and both pc's see each other and themselves as evidenced by the little computer icons and the name of each computer in the Network Neighborhood folder. One pc has 2 HDD the other 1 HDD. Neither is partioned.
However they don't see each others folders(and of course no files).
When I select Map Network Drive from the tool bar and type in the 'OtherComputerName' of the other pc I get an error as follows.(Same thing happens on each pc)

The following error occured while trying to connect
F: to \\OtherComputerName

The computer or sharename could not be found.Make sure you typed it correctly, and try again?


I've Ping'd each pc from the other and they see each other fine. The computer name is correct. Why does it say it can't be found?

One strange (for a newbie like me anyhow) in the Network Neighborhood folder there are as noted above the 2 little computer icons for each of my 2 pc's, but there is also a little Earth Globe icon for the Entire Network folder. In the Entire Network folder is the workgroup folder which for both my pc's is WORKGROUP. Inside WORKGROUP folder are the 2 little computer icons for each of my 2 pc's.

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Greenblatt is a pioneer-----------------------------------------

Before trying to map a network drive you most share the drive or a folder first on the other computer. You can share the complete HD or folder by selecting either object, then right click your mouse and select sharing and security. Follow the instruction and try mapping the drive again.

That's what I was missing (I couldn't see the trees for the forest).
Thank you verrry much!