That number (S-1-....) is how Windows 7 sees the old XP account.
Your old account doesn't exist on Windows 7, so it can't replace the number with a name.
You need to add yourself to the permissions list for that folder.
You can be owner of an object and also not allow yourself to have any access permissions.
How to add a "
Dumbo" user to the Security permissions on that folder (see bottom of post for a tutorial link).
Open "
Properties" > "
Security" on the folder.
Click on "
Edit"

Click on "
Add"

Type your user name into the text box.
Click on "
Check Names".

Click "
OK".
Make sure you have at least these permissions: - "Read & Execute".
- "List folder contents".
- "Read".
You may need to go into the "
Advanced" section (see pic 1) and apply the permissions for your user name, to the "
Child Objects".
Post a request if you need instructions on how to do this (hopefully you won't have to do it).
Have a look at this tutorial: Permissions - Allow or Deny Users and Groups