I guess this is actually 8.1, but you get the idea. In 2000/XP and even Vista/7 it was fairly easy to remove old wireless network profiles in case there was something wrong (ie bad credentials saved). Windows 8, unfortunately, made it significantly more difficult and requires the use of an elevated command prompt (start > cmd > right-click run as administrator).

Show all profiles
netsh wlan show profiles

Delete a profile
netsh wlan delete profile name ="PROFILEHERE"

Display the security key (if applicable)
netsh wlan show profile name="PROFILEHERE" key=clear

Stop auto-connecting to a profile
netsh wlan set profileparameter name="PROFILEHERE" connectionmode=manual