Toshiba can help you with that, given that the OS is usually OEM, meaning is tied to your system. You could write them or call them and they should be able to send you a replacement.
Short of that, you could purchase a Windows installation disk, and for the drivers, head on to Toshiba website, where you can find the drivers and utilities for your system. Download them on another PC, burn a disk or put them on an external drive, and after you're done installing the OS go ahead and re-install the drivers and utilities. It should give you a clean system.
If HDD failure war the original reason the system crashed (as it is most of the time), I recommend replacing it before you do all that.