You need to re-assign permissions on your temp folder:
*Stop and Restart the Windows Installer Service:
1. Click the Windows menu button (formerly the Start button) or press the Windows button on the keyboard.
2. In the Start Search box type Services and then click the Services item that appears at the top.
3. Expand the Services window and then scroll down to Windows Installer.
4. Right-click the Windows Installer list item and then click Stop, right-click again and then click Start.
*Add the Everyone group with Full Control permissions to the Permissions list of the default temporary files folder:
1. Click the Windows menu button (formerly the Start button) or press the Windows button on the keyboard.
2. In the Start Search box type %temp% and then click the Temp folder item that appears at the top.
3. At the top of the Explorer window, in the address bar, click the folder to the left of Temp in the folder path (Local by default).
4. In the folder list, right-click the Temp folder and then click Properties and then click the Security tab.
5. Click the Edit... button and on the next screen click Add.
6. On the next screen, in the large text window type Everyone and then click Check Names - Everyone should then be underlined.
7. Check the box for Full control under the Allow column, and then click OK, then OK again, and OK again to close all the windows.
*Run the Office 2007 installation again.
