This can be done by reinstalling Windows from the CAB files.
Method 1: (when you cannot access the Windows Desktop)
1. Insert the Recovery CD to boot on it. Shutdown the machine COMPLETELY by sliding the powerswitch towards you and holding it for at least five seconds.
2. Immediately start pressing F8 several times after switching on the machine, until you enter the Boot Menu.
3. In the Boot Menu, choose nr 6: "Safe Mode Command Prompt Only".
4. You will see the A:\ prompt, which in fact now represents the CD-ROM drive.
5. After the A:\ , type C: and then press Enter.
6. After the C:\ you should type "cd windows\options\cabs\setup" (without quotation marks)
7. It will now take about 20 minutes to reinstall Windows.
This just reinstalls Windows: all the other software you've installed will NOT be deleted!!
However, it is best to write down your settings for Dial-Up Networking (for example for your Internet access) and for your Network connection, as they will be lost.
Remark: if this does not work , retry but at the end of the line replace "setup" by "setup /is" to ignore Scandisk.
Method 2: (When you can access the Windows Desktop)
1. Click on Start- Run.
2. In the Run dialog box, type "c:\windows\options\cabs\setup" (without quotation marks).