Try this
Restart the computer in Safe mode.
For instructions, read Starting your computer in Safe mode.
How to Start in Safemode - Restart your computer.
- Before the windows logo you should gently tap the F8 key repeatedly until you are presented with a Windows XP Advanced Options menu.
- Select the option for Safe Mode using the arrow keys.
- Then press Enter on your keyboard to boot into Safe Mode.
Re-Setting Permissions- On the Windows taskbar, click Start > My Computer.
- Right-click the icon for Ext. Drive, and then click Properties.
- On the Security tab, in the Name box, click Administrator.
- In the Permissions list, check Allow for all items in the list.
- In the Name box, click System.
- In the Permissions list, check Allow for all items in the list.
- Click OK.
- Restart the computer.