Why does APPLE try to force everyone to use iTUNES. Isn't this anti-competitive? Is this legal? Is this an issue that is temporary until Media Center has a workaround?
It
is not illegal to be anti-competitive unless you are legally found to hold, and have abused, monopoly power over an entire market, and even then it is "iffy". Companies are anti-competitive all the time. That's what they do.
Apple is under no
legal obligation to support other media player software with their hardware any more than Microsoft is under a legal obligation to support using a Zune with OSX or Linux (hint: they don't). Now, the fact that they lock it down so much is certainly an a**hole move, and is anti-consumer, but there is no law about that. They are free to make their products as they see fit. Sometimes companies use this freedom to do jerky things, but other times they use it to make nice products (and in Apple's case, I'd argue that often the result is both).
The point is that you are under no obligation to buy their products. If enough people cared, and stopped buying iProducts, Apple would change its behavior. That's called free market capitalism.