Any bootable disk will do to boot. Could be a Linux one for example.
But let me assume you mean something like a "Recovery DVD" to bring your system back to it's original factory state.
Most likely it came with the machine, either as such or as 2 DVD's (a Vista OS DVD and something like 'Drivers and Utilities'.
Or it came on a recovery partition you can boot from by pressing some key combination at boot time (that's what Dell usually does).
Or you were offered to make one when you first started the system and you forgot to do that or you mislaid the disk that came out of it. Then it might be possible to to that right now.
If none of these possibilities rings a bell, first check the documentation that came with the laptop, then contact Toshiba Custome support to order that disk. Won't be free.
How do I get one for my laptop? It's a Toshiba, Satellite 305, with Intel(R) Core(TM)2 Duo CPU T5550 @ 1.83 GHz, 32-bit Operating System. Windows Vista Home Premium, Service Pack 2. I have a problem with connection when things get unresponsive, and icons get frozen on the desktop.