Your PC should have come with a disk set, if not there could be a hidden partition to restore, when you turn on the PC it will give you an option to hit a key to start the process. If don't have either one, contact HP, they can send you a restore disk, for some cost to you however.
Hi i'm having the same issue, i have Hp Pavillion dv6700 which is currently out of warenty. It came with Vista, i installed the trial win 7 and now it's done and i want to get back to vista, but the F11 doesnt do anything when i start it up at HP logo screen. Also, the system restore from windows only has like 3 entries that are within the last month. Is there any other way to do this? i cant even contact HP cause my laptop is not in warrenty and i feel like i really shouldn't have to pay for vista again, considering it came with my computer. Any help will be super apreciated