The first thing you should know is that on any OEM machine you can only reinstall the same edition of Windows that came pre-installed on it. (32 bit or 64 bit does not matter but no different Windows edition.)
You can change the HDD on your original machine and also RAM (if compatible.) (Sorry if I do not understand why you want to change the RAM too.)
If you do a clean install, you have to do it with Windows 7 Home Premium and then activate it using the COA key on the sticker of the machine which also indicates the Windows edition to which it is licensed.
Of course, you can obtain the Recovery CDs for your dead machine from Toshiba ( hmmm.... you can also get it from a benevolent friend who has the same model with the same Wndows 7 edition) and do a reinstall in which case it will preserve the OEM activation and auto activate.
The choice is yours.