Then im afraid you will have to use the Factory Settings to re-install windows....
This is how you put it back to Factory Settings...
1) Press and Hold the F11 key during boot.
If you are unable to get into Windows to start the recovery then you start the process when you first switch on the PC.
As soon as you turn on your PC, tap the F11 key on the keyboard until you get the "Windows is loading files..." message. When Recovery Manager has loaded click advanced options. Choose system recovery.
If you wish to try and backup any data then choose backup your files first and follow the on screen instructions. To run the recovery without backing up your data choose to recover without back up.
The recovery will launch and restore your system back to it's factory default state.
This is how you put it back to Factory Settings from desktop...
1) You can start the recovery from within Windows as follows:
Click All Programs
Click Recovery Manager
Click Recovery Manager again
Click next when the Recovery Manager program loads. You will be prompted with several questions before the recovery starts.
"Would you like to perform a program recovery?" - choose no
"Would you like to perform a driver recovery?" - choose no
"Would you like to launch Microsoft System Restore?" - choose no
"Would you like to recover your computer to its original factory condition?" - choose yes
The computer will now restart and launch the recovery program.
NOTE: Some computers are F10.
1) Turn on the computer
2) Start tapping/pressing F12 for Boot Menu
3) Insert HP Recovery Disc
4) Select DVD/CD-ROM and press enter
5) Press any key to start the installation
HP: 1-800-474-6836 (Call To Order Recovery Disc Set)
BEST OF LUCK!