Hi
Please filn the link below
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&dlc=en&docname=c01443317
run the Startup/System test, Memory test & Harddrive test if all the tests pass then you can use the disk you have got for windows 7 and install it
For more info
http://www.dedoimedo.com/computers/windows-7-install.html
PS : To boot from the Cd use F9 or the Esc Key on startup