Logon Failure - using Taskkill.exe

I have 2 peer-to-peer networks, both using a mix of XPPro and XPHome.

When I try to use taskkill.exe to kill a process on another system (from an
XPPro machine) I first get asked to enter the password for the system that
I'm on - rather than the one on the system that I'm trying to kill the
process on. Once I do that, I get the following error message:

Error: Logon failure: Unknown user name or bad password.

Here's an example of the syntax that causes this:

taskkill /s cindy /f /im notepad.exe /t

When I press enter, I get this....

Type the password for PUTZ\FUBAR:

This is the machine I'm working on - not the one I'm trying to use taskkill
on.

When I enter the password and press return, I get the above error message?

Since I'm a networking neophyte, nothing has been done with these networks
other than to set them up with the Windows Networking Wizard.

Any help would be sincerely appreciated!

- John