In your dual boot, all the boot files are on C. D has no boot files. If you don't mind the drive letter changes, try the following.
Your hdd where XP is installed needs 3 files: ntldr, ntdetect.com and boot.ini
Ntldr and ntdetect.com are in the i386 folder on the XP CD. They are also on the ME partition.
Reinsert your ME hdd and boot into XP.
Copy the 2 files from the CD or from C drive to the current D drive (so that they become d:\ntldr, d:\ntdetectcom) - copy, not move the files.
The boot.ini file, you can either use XP's Recovery Console (bootcfg command) or do it manually using Notepad.
First have a look at the existing c:\boot.ini file. click Start, Run, type c:\boot.ini and press Enter. Just have a look at the format of the text file. Don't change this file. Close this file.
In Notepad, create a new file by typing:
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /fastdetect
Save it as d:\boot.ini (DO NOT overwrite c:\boot.ini).
Click Start, Run, type diskmgmt.msc and press Enter.
Right click your XP partition and see if there is an option to mark partition as active. If so, select it. I suspect it's greyed out, that's OK.
Turn off computer. Disconnect ME hdd. Set XP hdd as master. Restart to see if it will load XP.
If it doesn't load XP, post back error message.
But in the meantime, you can insert XP CD and restart from CD. Press R for Recovery Console, press 1, Enter, enter Administrator password (if you have no password, leave it blank). At the prompt, type:
and press Enter. Note the drive letter of the XP partition. It should be C. Type:
and press Enter, where x is the drive letter of XP partition. Confirm. Type:
and press enter. Confirm. Type exit and Enter to restart computer. Remove CD to let computer boot from hdd. See if it works.
As you said, XP will become C, and you'll take a long time changing desktop shortcut properties and registry references from c:\ to d:\ and so on.