Hello and welcome to Bleepingcomputer.
You did not post your system make and model number, if you can provide that information that would be great!
Being that your monitor is going to sleep before any operating system is installed is a possible indication that your system BIOS is putting the monitor to sleep.
To stop this from happening, next time you boot up your system look on the screen for any prompts to enter setup, it may be F2 or DELETE.
Once you are in your BIOS setup utility, look for a possible menu heading called POWER or POWER MENU.
Look to see if any options are available that relate to the monitor or a possible mention of suspend mode or video off mode.
Check to see if any of those options are active or enabled, if they are select and change it to DISABLED.
Save the changes and exit.
Try installing your operating system again, in doing so, if you are installing Windows XP or up in NTFS format, there should be an option when booted to the installation disk to view any partitions or volumes which have windows installations on them.
It is here that you should be able to delete or remove any partitions that are on the hard drive.
If you really want to wipe the drive clean before installing another copy of windows, you can use one of two free partitioning programs to view the hard drives and delete those partitions.
Those programs can be downloaded as ISO images and burned to a CD-R disk and when completed, they can be booted to when the system is started up.
Here are two such programs listed below.
G parted http://gparted.org/download.php