RAID configuration on 845 AR

Question

I have the following arrangement:
IDE1 - (C: ) Seagate Barracuda 7200.8 (ST3300631A) - 300 GB, Ultra ATA/100, 7200 rpm, 8ms seek, 16 mb buffer
IDE2 - (D: ) Western Digital (WDC WD273BA) - 27 GB, Ultra ATA/66, 7200 rpm, 2 mb buffer
IDE3-4 - (E: ) Pair of 80 GB striped drives
I put the OS on (D: ) figuring I'd leave it as a dedicated OS drive and would put commonly accessed apps/games on (E: ) the RAID array and just let (C: ) be for multimedia storage and backup.  Well, I'm not happy with the performance of (D: ) as prior to the failed OS upgrade, my system screamed with the OS on the RAID array. So... I tried to reinstall the OS by unplugging the small drive (D:).  I then reinstalled XP on the RAID array which was drive D:. 
I assumed that by plugging back in the small drive, that the XP boot files would find the latest OS was on the RAID drives and leave them as drive D: and the small drive would be drive E:.  Not so, the current system resembles that of the configuration above and still boots the OS off the old, slow, small drive. 
Question: I'm pressed for space and cannot blow away either the RAID or the large storage drive C:  can I force the BIOS to change the small drive to go to drive D?  Alternatively... how would I reinstall XP onto the RAID without damaging/moving current data?
Boot.ini on drive c: says:
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(1)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(1)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

Answer 1

Ok... I'm missing something.  Pulled the Seagate 300 and WD 27 offline.  I booted from the XP CD, entered repair console and used "FIXMBR" and "FIXBOOT" commands on the array without blowing away existing file structure.  However, on reboot with just the array I get the following:
"boot failure from previous device
reboot and select proper boot device"
Googling around didn't reveal much.
Two ideas:
(1) Backup the WD 27, boot to recovery console and blow it away.  On reboot/format - will it become drive E:? or remain drive D:?
(2) From http://support.microsoft.com/kb/223188 "Change the System/Boot Drive Letter" (pasted below)  I assume the boot.ini file on my Seagate 300 is pointing to the volume on drive D: and the system boots whether the WD 27 or RAID is drive D:. 
Could I use regedit :gasp: and change the the drive designation for my WD 27 from D: to H: or something?  Then on reboot, the RAID array would assume drive D: and boot from the OS there?
1.   Make a full system backup of the computer and system state.
2.   Log on as an Administrator.
3.   Start Regedt32.exe.
4.   Go to the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
5.   Click MountedDevices.
6.   On the Security menu, click Permissions.
7.   Verify that Administrators have full control. Change this back when you are finished with these steps.
8.   Quit Regedt32.exe, and then start Regedit.exe.
9.   Locate the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices
10.   Find the drive letter you want to change to (new). Look for "\DosDevices\C:".
11.   Right-click \DosDevices\C:, and then click Rename.
Note You must use Regedit instead of Regedt32 to rename this registry key.
12.   Rename it to an unused drive letter "\DosDevices\Z:".
This frees up drive letter C.
13.   Find the drive letter you want changed. Look for "\DosDevices\D:".
14.   Right-click \DosDevices\D:, and then click Rename.
15.   Rename it to the appropriate (new) drive letter "\DosDevices\C:".
16.   Click the value for \DosDevices\Z:, click Rename, and then name it back to "\DosDevices\D:".
17.   Quit Regedit, and then start Regedt32.
18.   Change the permissions back to the previous setting for Administrators (this should probably be Read Only).
19.   Restart the computer.