"Access denied" when opening files or folders created in Windows 7 fro

Disable simple file sharing of Windows XP

1. Click Start, and then click My Computer.
2. On the Tools menu, click Folder Options.
3. Click the View tab.
4. In the Advanced Settings section, click to clear the Use simple file sharing (Recommended) check box.
5. Click OK.

Take ownership of a folder 

1. Right-click the folder that you want to take ownership of, and then click Properties.
2. Click the Security tab, and then click OK on the Security message (if one appears).
3. Click Advanced, and then click the Owner tab.
4. In the Name list, click your user name, or click Administrator if you are logged in as Administrator, or click the Administrators group. If you want to take ownership of the contents of the folder, select the Replace owner on subcontainers and objects check box.
5. Click OK, and then click Yes when you receive the following message: You do not have permission to read the contents of directory folder name. Do you want to replace the directory permissions with permissions granting you Full Control? All permissions will be replaced if you click Yes.
   
   Note folder name is the name of the folder that you want to take ownership of.
6. Click OK, and then reapply the permissions and security settings that you want for the folder and its contents.

How to disable simple file sharing and how to set permissions on a shared folder in Windows XP http://support.microsoft.com/kb/307874
Troubleshoot "access denied" when opening files or folders  http://windows.microsoft.com/en-US/windows-vista/Troubleshoot-access-denied-when-opening-files-or-folders