Last Spring I picked up a gateway with XP media Ctr loaded. It was cheap and is more than my kids need to meet their needs. It does do one quirky little thing that is annoying. When shutting it down I often have to click on Run, Turn Off Computer twice to get it to shut down. This also happens frequently wehn logging off one user to go into another user. I run McAffee, SPybot, and Adaware just like on my non media center PC. Never pops up anything so am reasonably sure it is not that.
It is on a wireless linksys system which has had some issues. Mainly loosing connection if you let the PC sit for a while and have to log back in. Have received a couple of error messages linked back to the linksys software too but those seem to be resolved.