oDin is wrong and right.
But if you do some research on netbui you'll find that it's not recommended, very bad security whise.
You didn't provide enough information so I'm going to have to assume some things and ask you one question.
First the question. How are these computers accessing the internet? Both have same connection dsl/cable or phone line etc? no internet connection available?
I'm going to assume you have an internet connection between the two computers.
Here is the problem. One is win98 and one is windows nt based system.
Here is two ways to solve it.
1.) Requires logon, but more security.
You have to turn on the client for microsoft networks on both machines. (Most likely already done)
Change the way the windows 98 computer logs on. (Use Client for Microsoft Networks) Have it log on using a unique name and password.
Create an account on your windows Xp system with that exact same logon name and password.
(For XP)
Go under the folder options and go way to the bottom and turn off the simple sharing.
Then go into the sharing and security options for the folders you want to share.
There is an option for permissions. Chose this and go to add. Chose advanced, choose find now. Add the user account for the other computer. For exampe the user bob should be. Computer Name\Bob
Go under the security tab and then add that user again under this setting and choose what access you want the user to have.
Using this method you can observe what actions are being carried about by the other user. Although this setting is in practical because most likely he's sitting right next to you and you can see what he's doing.
(Win 98)
You just need to choose a folder to share and share it. No extra settings or securities need to be set.
2.) No logon.
Client for microsoft networks needs to be installed.
Choose windows logon for windows98 version.
No new accounts need be made on windows xp system. Multiple user accounts will bring up logon screen.
Go under Folder Options turn off simple sharing. (sorry never understood the simple file sharing so I have to turn it off) haha I know how to do it the hard way and not the easy way. *shakes head*
Under permissions for your new shared folder make sure that the account everyone is added.
You may need to add this account under security, but I think by default it's already there. You can then change it's permissions if you wish under security.
Click apply done done whatever. After this is done you should be able to access and no reboot is necessary.
You should have been able to access your windows 98 machine, but not vice versa.
There was a program that needed to be installed from the windows xp system on the windows 98 system. Remember it asking you to make a network disk to be installed on non xp systems? Yeah make sure you do that.
Go to bottom for more information if you do or don't need the following step and your problem isn't solved yet.
--Only relevant if you have no internet connection---
Don't do the following if you have an active internet connection.
If you are using two computers that do not use the internet in anyway you need to configure your tcp/ip settings. This is preferred by everyone except like 10 people who prefer net/bui.
netbui was the first method used and has been deemed by microsoft as insecure and is never installed by default, but is placed on the cd anyways in case some people are adament about using it.
Use tcp/ip.
To use this method you must obtain your ip address for you windows xp system. by going under the network connections it tells you on the left when the folders option is uncheckeded. It can also be obtained under by going under network connections, right click on the local area connection properties. Under the this computer uses the following connections. choose the tcp/ip properties. It tells you your ip address being used and your subnet mask. Very IMPORTANT. On your windows 98 machine go under this same setting and check it. Choose use the following ip address.
Make the windows 98 ip address one higher then your windows xp system. Example
XP> 101.101.101.1
98> 101.101.101.2
the subnet mask has to be the same, usually 255.
ex.
xp> 255.255.0.0
98> 255.255.0.0
When this is done choose apply. This may require a restart, don't remember.
this should fix your problems.
----Misc---
These are some misc network facts that may prevent a connection.
Computer names need to be unique.
Under System settings there is a tab for computer name. I don't remember where it is under windows 98. Look under system.
Workgroup names need to be the same. Don't remember how to change them. If this is a problem you can change them by running the network wizard again.
This shouldn't be an issue though. Since you can see both computers listed. I only mention it because it's network related and because the previous person mentioned it. Multiple networks can be created using different workgroup names, but this prevents computers from seeing eachother. Probably a security thing.
For added security use a unique network name.
Laters