Neither Vista nor XP boots

[Sdream]

Desktop computer with 2 HDDs:
One Hitachi SATA2 originally in computer
and partitioned C & D
One WD Caviar SATA1 which I added on
and partitioned F & G & H

Vista is installed on C of Hitach SATA2
Ubuntu was on H and Win XP was on F of WD SATA1

EasyBCD reinstalled Vista MBR
I removed Ubuntu
Then EasyBCD established a dual-boot of Vista and XP

Everything was fine so far
Bur the IDs of the partions are all changed
C & D changed to E & F
F & G & H changed to C & D & G

I tried with EasyBCD to restore them back to their original IDs
After 2 or 3 experiments
Computer does not boot
Win XP desappeared from the bual-boot list
Vista is still in the list but does not boot

Help please

Thanks

[Terry60]

Where did the letters change ?
Remember, disk letters don't exist in the real world. They're not attached to partitions physically.
They're just entries in the Windows registry - figments of the imagination of the running system.
All Windows systems will see them differently except by coincidence or user action.
Having said that, if a system which installed as one letter, gets changed, it will break the OS because the registry contains thousands of entries pointing to the original letter.
You can "unchange" a letter (i.e. put it back to what it was at installation) using this hack for Vista, but unfortunately XP doesn't get far enough to use regedit in the same way.
Read this for XP.
EasyBCD has absolutely nothing to do with setting disk letters.
There are no letters in the BCD, just UIDs.
EasyBCD translates the UIDs to the letters currently seen by the running system for your convenience.
If you change any of the letters, you are effectively lying to the boot manager about where to find the systems, hence why nothing will now boot.
First check that you haven't reversed the boot sequence of the HDDs. That will cause the lettering algorithms to detect the partitions in a different order and letter them differently. (Tip - always give your partitions letters manually, don't let the system default them. That sets them in stone, and a shuffle of hardware won't affect them)
Put Vista back to the letter that last worked. Use regedit to put Vista back to the proper letter if the system fails to boot completely.
Install EasyBCD 2.0 latest build, remove and readd the XP entry, letting Easy2 auto-configure the XP boot.