locked out of certain folders/files after networking XP and Vista

Hi, total networking novice here, but I did successfully manage to get
my 2 vista machines to see and talk to my one XP machine. However,
there are a handful of folders on my older XP machine that I have
somehow completely locked myself out of. Most of them work in
general, but these select few now will not open from any computer -
not even from the original XP machine that they were created on. I
really need access to some of these and seemingly can not get to them
at all anymore.

Any thoughts would be more than greatly appreciated. They are not
password protected at all and there are no permissions set on them
either.

Thanks in advance!