I got MCE on a P4-3.6Ghz, although at this time, I too am running XP64.
The MCE, I feel, is quite honestly a pile of pooch-plop.
Its basically WinXP Pro, but with lots of useless junk bodged onto it.
Its slower than Vanilla XP, and this is probably due to all the junk... On my version, thankfully, it can all be removed, but its still not as quick as if I had just installed XP on its own.... I have tried a couple of customised installs based on the original CD, starting with simply disabling stuff, up to completely removing the Media Center folder altogether, but no matter what I do, it fails to install, so I am annoyed at that ( Myself? ) for that.
This is mainly due to the fact that the CDs I have for MCE are specific to that PC, and also has its own idea of whats needed, so the normal version of MCE should allow for "adjustments".
Now, the Media center extras that you do get are pretty much available in other prorams... ShowShifter is one that rings a bell, as is creative media player too! - although I have a few Creative cards with the drive bay extra hardware junk, and the LiveDrive IR and the Audigy 2 and the XFI all have remote controls, I have found that the software on those also kill off any chance of me having a half decent performing PC, so I dont use them... Basically MCE has turned my 3.6Ghz P4 into a 1Ghz Celeron, and the creative software has turned my 3Ghz AMD64 into a Duron, so I have opted for a fresh install with absolutely no junk for the remote controls... PERIOD.
Hell, dont get me wrong. Having a TV card in a PC is fine. Useing a PC for all your Media is just fine, and as long as there is no silly junk for bone idle users, there is nothign stoppign your PC from doing anythign you could ever wish it to do, and have all *** speed in the world, but seriously... As soon as you take that idle road and add a remote control to it... Kiss any possibility of performance goodbye.