By this statement, I assume this to mean that you:
- Failed to make recovery disks as per the maintenance recommendations when you purchased the machine; or
- Made the disks are recommended, but have since lost or misplaced them; or
- got the machine second hand and never was given the recovery disks.
The good news is, you can order a restore CD/DVD from HP. The bad news is, that the only recovery option is Windows VISTA, which apparently is what the machine came with. If you need a newer version of Windows than VISTA, you are pretty much out of luck. You will need to purchase a new OS, or reload your OS with whatever media you have and perform a new, clean load. Once you get everything back the way you want it, either purchase a good system recovery software package, or use one of the alternatives on the freeware market. Just be advised that not all recovery software is created equal; some will only work if you can boot the system and then run them. The good ones provide a self-bootable disk to allow you to restore the disk to the image saved.
If VISTA is good enough for you, go to this link and under software option you'll see recovery disk.
HP Customer Support Software and Driver Downloads