[WPKenny]

in ubuntu you want to do something like "connect to folder" I think.

Then type in the box:

smb://[xpmachine's ip]/[name of shared folder]

And I think that should do it.

Oh and you might want to enable the Guest account on the XP machine just to be sure. (control panel...user accounts)

EDIT:

Ok above is how it's done on a mac. Not very helpful to you.
On Ubuntu you want to connect to server and select Windows Share and type in your xp machine's ip.