[flash8pro]

One question: is the Swedish version of XP you are running XP "Home" or "Professional"?

Am I understanding correctly that even the user account that created the folders (on the computer sharing the files) can no longer view them?

When I have experienced a similar error message in the past, it was because the user account I was trying to access the folders from was not password protected. If a user account is not password protected, XP thinks of it as "not having the authority" to do certain things, even though it should be able to. If you are not keen on typing in passwords to log on to Windows every time you boot, use the autologon feature in TweakUI.

Without knowing more info, my guess would be that the account(s) you are trying to access the folders from are not password protected.