mapping a drive on an xp computer to a vista laptop

the error i get it that it keeps telling me that i do not have access. i have read a lot of other posting about this issue, but none of the solutions has worked. and my error seems a bit different. i can see the XP computer, as well as all the other xp computers on the network, and they can see me. they can even access files on my shared folder. the folder i am trying to access on the xp computer is password protected, using the same username and login as onto my vista machine. i can connect to the commputer (the drive icon is green not red) but when i try o open it to view files stored there i get a message saying that access is denied.
any help solving this problem is enourmously appreciated!