Some of your system is very marginal to run XP, particularly the HD capacity and the RAM. XP is very hungry for both.
It might be a good idea to go back to ME to make sure you can get this up and running again. If you do, then use an ME startup disk, and format your HD before trying to install a fresh copy of ME.
Keep an eye open for unfavourable changes you may have made to the BIOS and if in doubt revert to the factory default settings.