Like other Presarios, the Presario C300 comes installed with a Recovery Partition---a separated chunk of your hard disk containing all the tools to recover and reinstall the operating system and other factory-installed programs and files should your system suffer a catastrophic failure. You can run the recovery software from Windows easily, but it's possible that whatever problem you're having with your system may prevent Windows from booting, so you can also access the software installed on the Recovery Partition immediately upon computer start-up, without having to go into Windows.
Click "Start" and type "recovery." When "Recovery Manager" appears in the search field, click it.
Click "Advanced Options," "System Recovery" and then "Next" to tell the PC to restart and bring up the Recovery Manager on start-up. (On Windows 7, simly click "System Recovery," and click it again when the computer restarts.)
Click "No" if asked to use the Microsoft System Restore program.
Click on the "Back up your files first" option if you want the user data on your hard drive's primary partition to be backed up before that partition is wiped. This is recommended. Only leave it unchecked if you are OK with the deletion of all of your data or if the drive has become so badly corrupted or infected you can no longer use the data.
Click "Next" and the recovery process will begin.
Turn on the computer and wait for one of two things to appear: a message mentioning the BIOS, or an HP logo. Press "F11" quickly.
Select the "Back up your files first" option just as you would in the Windows application.
Follow the on-screen instructions to restore your system.