I have some shared folders in the list in 'Computer Management' that point to folders that dont exist anymore. But Windows wont let me remove them, "The system cannot find the path specified", maybe a net * command through the console could solve it?
Shares are listed in
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Shares registry key, you can delete the entries there, after a backup of the key (source)
Make sure you remember that you've NOT used a removable drive or a CD to share folders off those drives. If you in fact did share folders off those drives, you can mount that drive (USB-in the HDD or insert the CD with those previously shared folders) and remove the shares using normal Windows Share menu (Advanced Share) options.
If you no longer have that removable drive - then delete the keys in the registry.