Last week, I decided that this weekend, I was going to wipe all of the preinstalled crap off of my MCE PC, and install Windows XP Media Center Edition 2005. I didn't want to wait for my copy from HP, so I decided to use my copy from MSDN while I waited.
Mine was an HP M495C, so your mileage may vary. However, the basic instructions should apply to any HP.
NOTE: These instructions involve potentially violating the license agreement that accompanies your MSDN subscription.
1) 11 blank CD's;
2) The C:\HP folder on your MCE backed up to a seperate DVD or a seperate computer;
3) The Windows XP Media Center Edition 2005 ISO images from your MSDN subscription;
4) About six hours to burn;
5) (optional) InterVideo WinDVD 6.
Step 1: Run the HP Recovery Disc Creator utility to create a set of recovery CD's in case everything goes to Hell. This will use 9 blank CD's.
Step 2: Using your favorite CD burning software, create CD's from the two MCE 2005 ISO images. That will use your two remaining CD's.
Step 3: Make sure you have backed up the C:\HP folder. If you do not see your C:\HP folder, do the following. Open Windows Explorer by hitting Windows-E. Go to Tools->Folder Options. On the View tab, pick "Show Hidden Files and Folders" and uncheck "Hide protected operating system files (Recommended)."
Step 4: Boot from MCE CD #1. Go through set up normally, but do not repair the existing install. I recommend deleting the C: partition and recreating the partition again. I left my recovery partition because I didn't want to mess up any other crap that HP had in the BIOS.
Step 5: When asked to insert "Windows XP Professional CD 2," insert MCE CD #2.
Step 6: When asked to insert "Windows XP Professional Service Pack 2 CD," insert MCE CD #1.
Step 7: Finish the standard post-install steps for Windows XP, then restore the C:\HP directory.
Step 8: Go into Device Manager (Windows-Break, Hardware->Device Manager) and look for all of the yellow warning signs. Right-click on each one and pick "Update driver..." Tell it to look in each subfolder of C:\HP\Drivers one-by-one for the drivers. When it finds one it likes and installs the drivers, wait. Several will have other "Unknown" devices be found afterwards. Have it look for those drivers in the same folder that you just pointed it to. Repeat step 8 until you no longer have any yellow warning signs in Device Manager.
Step 9 (optional): Install InterVideo WinDVD 6 if you want to be able to play back DVD's.
Step 10: Reboot and enjoy.
Now all I have to do is install TweakUI so that I can automatically login my TV user, and I'm done.