Additional tips:
Remove any "Wacom", "Touch" or "Pen" devices from the Human Interface Devices section of Device Manager before installing the Wacom driver. Empty temp files in both the Windows ("C:\Windows\Temp") and User directories ("C:\Documents and Settings\<User Name>\Local Settings\Temp" for XP; "C:\Users\<User Name>\AppData\Local\Temp" for Vista). Make sure the "Program Files\Tablet" directory is emptied/removed.
Note: For the 'working run' I did this and also cleared all 'hidden devices' (see instruction below) then installed the 505-7 driver, found it didn't work, so then installed the 510-4 driver (without removing the 505-7 first!).
To remove 'hidden devices' from Device Manager (that is to thoroughly insure all mis-installs etc are removed) follow this:
http://support.microsoft.com/default.aspx/kb/315539
- when Device Manager appears, select menu option to 'Show hidden devices' then expand the HID section and remove all ghosted devices, plus all Wacom, Touch, Pen etc. Reboot and attempt new driver install. (Select to find device driver later if prompted immediately on reboot before you get chance to install the new driver).
For completeness: This was tested on a European (UK) Toshiba M750-10K with Pen & Touch running Vista Business (32-bit) (note the driver download includes a 64-bit driver too, but not personally tested).