If the hard drives don't appear in Disk Management, there's a good chance your system is infected. Is this why you want to do the clean install?
Are you booting with the Win 7 DVD, or trying to re-install while booted into Windows? Or using a Recovery Disk you created using the Toshiba tool?
The Toshiba should have a method to restore the system to the way it was when it left the factory, either using the Recovery disk set you created, or a Recovery partition. Check the User Guide for your system for the exact procedure. Often started by holding the 0 (zero) key down while powering on the system, or may be an option on the Advance Boot Options screen you get when tapping F8 as the system starts up.
You can download the User Guide for your system if you don't already have it from the Toshiba Support site
. Search the guide for Recovering the Internal Storage Drive
This usually deletes all your personal files
. Even if it has a non-destructive recovery option, you should have your files backed up, just in case.
You can also post in the malware forum, and have our experts help you remove any infection. They are always busy, so may take awhile for them to get to you.
Click this link: First steps
and follow the instructions there and post the requested info in the Virus/Trojan/Spyware Help Forum
, not here.
If you are unable to complete any of the steps, proceed to the next one, but be sure to note which step you were unable to complete, and include any error messages you received while trying to do that step.