IR blaster to turn on/off TV w/ HTPC?

You can probably use the "Learn" feature of the remote to program another button to act as the power button for the TV.

Some applications can also learn the button and send it.

I should know whether WMC can do this, but I don't. Sorry.

Take a look at Eventghost. You can use Eventghost to learn the IR Command to your TV based on a specific button on your current remote.

Try intelliremote, or lmgestion keymapping software. Theyre both a bit easier than eventghost.

Yes, this is possible through EventGhost, but sadly, probably not with your current IR blaster. Unfortunately, most IR blasters don't have transmitting plugins for EventGhost which means you will not be able to send IR signals to other devices.

However, with a USB-UIRT, you can fully control any IR component with EventGhost.

The cheapest and easiest solution will be to replace the remote you have with a $10-$15 Harmony 200 or 300 remote, and program the "power" button to toggle TV power.

P.S. you can still use the IR dongle that came with your current remote.

+1 on the Harmony suggestion. This will by far be the easiest way to do what you are asking and will probably be useful for other hardware you have as well. Logitech really needs to come up with a mouse function for a new Harmony though.

They have a mouse function but it sucks.

You should really just get a decent universal remote, such as the Harmony, and save yourself the time of trying to get your EventGhost/blaster solution working.

The IR codes for both your TV and WMC are already in their database so you won't even have to learn anything. You also won't have to learn and use another piece of software to try to get this working.

Another option may be to see if your TV's remote has WMC codes included.