Keep on prompting for credential

To save your SharePoint password: Add the SharePoint site to the Local Intranet Zone in Internet Explorer. To do this, go to Tools > Internet Options > Security. In Local Intranet, click the Sites button and then Advanced. Add your SharePoint URL. Click Ok. Go to Start > Run and type in "control keymgr.dll’" to open the Windows key manager. Add <your_sharepoint_site_address> with your SharePoint site login credentials. If this entry already exists, edit it to have your login credentials.  For Vista users, when using the key manager, make sure you select "A Web site or Program credentials" for the type of password, and if prompted to change your password, say "no" (unless you want to change your password). Enter your password and click OK. Reboot the computer. If you are missing the Add button, you may want to modify Windows Registry to be able to save the password. Note that for editing Windows Registry, administrator rights are required. Editing Windows Registry is not safe and you will perform it at your own risk. In Windows, go to Start > Run and enter "regedit". Navigate to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\. Find the DisableDomainCreds entry. A value of 1 (enabled) will prevent you from saving new credentials. Change the value to 0 and reboot. Now you should have the Add button available. Note that 0 is the default value. Also check the LmCompatibilityLevel entry. It should be set to 3, which is the default value. If you have another value, change it to 3. If it does not work with 3, then also try it with 2. Reboot the computer to apply changes.