Because I use Microsoft's Windows XP Professional on my primary computer at home, I was able to control that system -- and view its desktop -- from the Mac mini in the dining room. That was thanks to a program called Remote Desktop Connection for Mac OS X that Microsoft offers as a free download.
This is just an add-on to the internet browser. Windows XP has Norton PC-Anywhere built in. You can run your PC from anywhere you have net access. Do anything, run any program.