Only the machine that has both ubuntu & win xp installed on the same HDD is having the problem.
Of course it is - it's changed. There are all kinds of things that could have caused this - depending on what kind of windows network you have.
Can you access the windows network from Ubuntu?
I have the feeling that Ubuntu changed some permission along the way during the install and now windows can not overwrite it.
None of your windows data has been touched by the install process. (Assuming you defragged before resizing your drive?)
Windows networking can be very nice provided things don't change much. The simplest takes the form of a PTP network. But it could be one of the more complex ones, right up to an exchange network. I cannot tell what may have happened unless you tell me how it is set up.
It sounds like the KP computer has been de-registered with a controlling computer and it has asking to be re-authenticated. But I cannot be sure. Whatever, the request you see is not internal to the computer - it is coming from the computer hosting the "folder" you want to see.
Probably your best bet is to go through the process of adding the XP machine to the network all over again.