1) Key Manager: run the following command from Run or Commands Prompt:
rundll32.exe keymgr.dll, KRShowKeyMgr
2) Use the cmdkey utility from command prompt:

• cmdkey /list
  To show all credentials. Take note of the Target name
• cmdkey /delete:targetname

Example:
C:\Windows\System32>cmdkey /list
Currently stored credentials:
Target: REMOVE-ME
Type: .NET Passport
User: REMOVE-ME
C:\Windows\System32>cmdkey /delete:REMOVE-ME
CMDKEY: Credential deleted successfully.