Wiki or WebDatabase Forum for work

Hi all.

I am looking for the following features.

Easy to use,
Easy to make different level of security and groups
Preferably but not nessecary intergated with Active Directory for security.
Forums section
Wiki /FAQ Database section
Easy to install.

Needs to run on Windows 2003 sp2 IIS
I don't want to install Apache or other web servers, as IIS is being used already for other internal sites.

I am looking for a engine/template I can use for either a Wiki or Forum engine to track information and faq's to use internally in the company, but it will be accessable from outside of the office LAN, so I need to have a guest area as well as user authentication.

I have a license for MS SQL that I can use as well.

After suggestions of what people have used that is either open source, cheap or bought product.

preference is for open source or cheap.

thanks for all your comments in advanceStart Free Trial