Upgrade Problems XP from 2000

I just tried to upgrade my laptop from 2000 to XP.
Everything seems okay except for my local network. I have a
local network with 3 computers run through a router, each
with access to the internet via DSL. Originally this was 3
machines, 2 with 2000 and 1 with 98. Now it "is" 1 with 98,
1 with 2000 and 1 with XP.

I still have the network working with the 98 and the 2000
but I can't get the XP machine to recognize or be
recognized. All three access the internet without problem.
The error messages I get are: "\\Dell4100\C (for example)
is not accessible. You might not have permission to use the
network resource. Contact the administrator (me) of this
server to find out if you have access permissions.The
network location acnnot be reached. For information about
network trouble shooting see ..."

I have tried everything I can think of to no avail. One
possibility is I did the upgrade while logged on under my
name (I have admistrator privileges) and not under
Administrator.

Could that have caused the non-permission problem?
If not what might have?
If it is an "administrator" problem what solutions might
there be?

Dick