Vista - Password protected sharing

Hi. I want to share a partition on my computer over the home network. However, this partition contents secure information I'd like no one else to see. So, I tried Password protected sharing feature. From the other computer (OS Windows XP Professional SP 2) I tried accessing it via View Workgroup Computers, and it demanded a username and password. Using a username and its respective password from the partition-containing computer resulted in an Access Denied message (although the partition-containing computer was in a welcome screen state, with all user accounts unlogged, and the username and password were absolutely the same, even case-sensitive).

Now what's that supposed to mean, and can I somehow protect this shared partition with a password?

Still waiting for an answer...