I want to know what is the proceedure to enable me to get into the CMOS or BIOS on an HP desktop? I am trying to change the setup to boot from the DVD drive , so I can re-install the OS.

Check the user’s manual if you have it. You don’t list the model of your HP, but you can usually go to HP’s website and download a copy or read it online. A lot of PC’s use F2 to get into the bios, but it may be a different F key on yours. Watch the bottom of the screen during boot up, the setup F key is usually displayed there.

You want to reinstall the OS from the backup partition on your HDD? I think its F10. If you old OS is really messed up, do the advancted options choice where it lets you totally wipe out the old OS.