The procedure below was written for XP but should be similar for Windows 7.
It sounds as if the loaded driver has been corrupted and it will not be overwritten by a correct driver until it has been un-installed.
Please try this. Plug in the scope and then go to Windows Device Manager.("Control Panel", "System" and then click on the Hardware Tab). If there is an "Unknown USB device" there or a "PicoScope 3000 series" with a yellow warning triangle under USB controllers, left click on it once to highlight and then right click to bring up a list from which select "Uninstall". Once that is done, unplug the scope and then plug it back in again. The Windows "New Hardware Found Wizard" will run. Follow the on-screen instructions and, if the wizard asks to connect to Windows Update, select 'No' and allow Windows to automatically detect and configure your scope after which the scope should show up in device manager again but as a "PicoScope 3000 series Oscilloscope". If you get that, your PicoScope6 software should now work.
If that does not work, please contact us at helpdesk:-firstname.lastname@example.org