To 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 group. If you want to take ownership of the contents of that 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 press 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.
To take ownership of a file
1. Right-click the file 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 Administrator, or click the Administrators group, and then click OK.
The administrator or the Administrators group now owns the file. To change the permissions on the files and folders under this folder, go to step 5.
5. Click Add.
6. In the Enter the object names to select (examples) list, type the user or group account that you want to give access to the file. For example, type Administrator.
7. Click OK.
8. In the Group or user names list, click the account that you want, and then select the check boxes of the permissions that you want to assign that user.
9. When you are finished assigning permissions, click OK
For more information refer to microsoft article
http://support.microsoft.com/kb/308421
