Just to point out here. After downloading the Skype4COM.dll you will probably need to use regsvr32 to register the dll, that way inside Visual Studio you can add the .dll as a recognised COM Component!
regsvr32 C:\Windows\System32\Skype4COM.dll
for example, you will get a popup indicating it successfully registered it, and now back in your IDE, inside the Add Reference under the COM Tab you will see the Skype Library.
Hope this helps,
Andrew