I was wondering because I have a 2 year old 939 socket mobo and could theoretically finish building it into a HTPC. So I wanted to know what the advantages are, so please post them.

the main reason i use a HTPC to power my setup is because i can upgrade and customize it reletively inexpensively. Using software, you can also upscale your dvds without having to spend hundreds of dollars for a new piece of electronic equiptment. Plus, if you plan on using your system to watch HDTV, you can get a HDTV pci tuner card for much less then geting an external tuner, and a way to connect your equiptment to a VGA input.

The question doesn't really seem complete to me.
Advantages to using an HTPC as opposed to using what??

I use 2 HTPC's in my home.
One is the backend for itself and another.
All of my families digital media is stored on the backend HTPC server.
It is used as a DVR, DVD storage (DVD's we own ripped to disk), photos, music, etc, etc.
It is also the frontend HTPC for our primary family room plasma TV (the server is actually downstairs from it), and the other HTPC is a frontend to that same server for a Home Theater in the basement using a DIY projector.

So, if we want to watch live TV, we can via the htpc, as the backend has several tuner cards, or we can watch live tv direct from the tv's built in tuner. My wife and daughters regularly schedule shows to record and watch them when they want to, where they want to (the MythTV software I use has a plugin so that we can access the same content from any PC in the house via a web interface). My daughters mostly watch their recorded shows on their own computers.
We watch movies on it, it's DVD player is an external one sitting in the family room where the plasma is.
and the other HTPC also has a DVD player that can be used in the Home Theater with the projector.

I also have an external HDTV tuner attached to the HTPC and I can feed that content to either the plasma or the projector.

Advantages?? Media everywhere I might want it within the house.
Other advantages?? Not sure... I just mainly started working on it so that I didn't have to pay someone for a DVR service I guess.

Alright thanks ! Im really going to have to consider this !

Of course there are disadvantages too. For example, the media companies think that by using a HTPC your automatically a filthy dirty pirate that'd gladly be "robbing liquor store and selling crack and running over school kids with your car" just for giggles. Thus, they make it as hard as possible to use any of the cool new stuff on your pc unless you...
1) Only use windows Vista. (Stable as a skyscraper built on pudding)
2) Only use equipment that supports their DRM sca...er scheme. (ie, a new high-end graphics card, and monitor)
3) If you insist on silly things like exercising the rights the FCC says you have to use your own equipment for your cable service instead of a box supplied by your cable co, you have to purchase a PC from one of their approved manufacturers. (Luckily, those PCs will have been rigidly tested to work perfectly, right out of the box, for every consumer..... insert sarcasm here)
4) Of up want to watch something from an external HD source, such as a Blu-Ray, HD DVD, or PS3, forget it. Who cares if the consumer wants something to input those sources into his/her htpc? They'll ONLY use it rip off the struggling media companies.

So basically, an HTPC is awesome, provides wonder functionality, and saves space if you're a bachelor in a small apartment. (Threw the last one in because it's why I run one). However, the entire concept is stagnating and unable to grow due to death by drm.

Sorry, just felt like complaining.

I'm working on getting the Intensity black magic cards to work in linux and have the processor do real-time compression (more likely two pass compression realtime crunching and then a longer compression pass later). This would allow me to use a hdmi/dvi repeater/de-hdcp'r to then input whatever I want... will be a while though as I'm waiting on the guy writing the software

Im waiting for the world to wake up before ALL of their rights are gone...

Hey thanks alot guys, I will eventually build one as I can see it has numerous advantages. Thanks again. Peace.