Well, to get into the bios, hold "esc" as the system turns on, then press F1 when you see the "check system" message. However, there is no way to reinstall an OS in the BIOS.
If you want to reinstall windows, you have two possibilities. Make sure the boot order has the optical drive first and insert your Windows 7 disc. Reboot and follow the on-screen instructions.
The other option is SOME Toshibas have a recovery partition. To access the Toshiba recovery partition, power off the laptop. Hold down the 0 (zero) key and turn the laptop on. Keep holding down the zero key until the TOSHIBA logo appears, where you should start tapping the zero key repeatedly. Stop if the unit beeps or when the TOSHIBA logo disappears. The screen should flash ** HDD RECOVERY MODE ** for a split second, then load the Toshiba recovery program right from the hard drive.