My son has a hp mini laptop and got a virus can I wipe out the hard drive and start again? It does not have a cd rom drive how do I reinstall windows

Check to see whether there is a hidden partition which contains an image of the original operating system. Usually, you'll press <F11> or <F12> to boot from the hidden image. You will often see something that says "Hit <F11> to ...". If you have a hidden image, you should be able to use the functions on that partition to wipe the hard drive and fully install the operating system. You might have to get into the system BIOS (usually <F2> on bootup) to enable the message, but it's usually on by default.

Do you have a set of install disks (even though you don't have a CD Rom drive)? It doesn't make sense to me that you would.