Make a USB installer using the directions and tool from HERE. If you need an SP1 Windows image get the same version that you use (including 32 or 64 bit) from HERE.
Download all of your drivers from Toshiba support. Then boot from the USB installer, select custom install, delete all existing partitions and then install Windows to the remaining single unpartitioned space. Then load the chipset driver and all other device drivers, Windows Updates, and re-activate using the key off the sticker on your computer.