USB boot changes drive letters

[CDM6421]

Hi all, first post here, but decades long Spinrite user.
I'd stopped using Spinrite a couple years ago when it be came trickier to boot to DOS and see the drives. But this latest version piqued my interest as I'm now using an SSD for my system, or C: drive.
Funny thing is when I did manage to boot the bootable USB as a test it changed my C: to H: rendering my computer unable to find Windows. Fortunately I was able to repair it and now back to normal. But I'm seriously wondering if I should continue.

I suspect it's because I have a variety of hard drives installed and (I think) BIOS decides what letter to assign based on the interface. And IIIRC when I first built this about ten years ago I needed to disconnect all but the SSD to get it to be the C:

Anyone else see this happen?

System details:
Windows 7 Home Premium
ASUS Sabretooth 990FX, v. 1
C: - Mushkin Enhanced Chronos, SSD, SATA
D: - Hitachi Ultrastar, HDD, SATA
E: - ASUS DVD read/write, SATA
H: - Hitachi Ultrastar, HDD, SATA
I: - Western Digital, HDD, IDE

I'm adding on an excerpt from a CPU-Z system report which shows the system's drive assignment order:

Storage
-------------------------------------------------------------------------

Drive 0/0/-1/-1
Device Path \\?\scsi#disk&ven_wdc&prod_wd1600jb-00gva0&rev_800.#5&369b2b6d&2&000000#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
Name WDC WD1600JB-00GVA0
Revision 08.02D08
Serial WD-WCAL91038588
Capacity 149.0 GB
Type Fixed
Bus Type RAID (8)
Features SMART
Controller IDE Controller at bus 3, device 0, function 0
Link Speed PCI-E 1x @ 2.5 GT/s
Volume i:\, 149.0 GBytes (74.2 percent available)

Drive 1/1/-1/-1
Device Path \\?\scsi#disk&ven_hitachi&prod_hua723020ala641#4&fa535c2&0&000000#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
Name Hitachi HUA723020ALA641
Revision MK7OA840
Serial YGHEY7PA
Capacity 1863.0 GB
Type Fixed
Bus Type SATA (11)
Rotation speed 7200 RPM
Features SMART
Controller Serial ATA Controller - AHCI at bus 0, device 17, function 0
Volume h:\, 1863.0 GBytes (29.2 percent available)

Drive 2/2/-1/-1
Device Path \\?\scsi#disk&ven_mknssdcr&prod_240gb-dx#4&fa535c2&0&010000#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
Name MKNSSDCR240GB-DX
Revision 609ABBF0
Serial MKN1234A0000122060
Capacity 223.6 GB
Type Fixed, SSD
Bus Type SATA (11)
Features SMART, TRIM
Controller Serial ATA Controller - AHCI at bus 0, device 17, function 0
Volume c:\, 223.5 GBytes (24.3 percent available)

Drive 3/3/-1/-1
Device Path \\?\scsi#disk&ven_hds72404&prod_0klsa80#4&fa535c2&0&030000#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
Name HDS724040KLSA80
Revision KFAOAC6A
Serial KRFS06RAHLNPTD
Capacity 372.6 GB
Type Fixed
Bus Type SATA (11)
Features SMART
Controller Serial ATA Controller - AHCI at bus 0, device 17, function 0
Volume k:\, 372.5 GBytes (58.5 percent available)

Drive 4/4/-1/-1
Device Path \\?\scsi#disk&ven_hitachi&prod_hua723020ala641#4&fa535c2&0&050000#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}
Name Hitachi HUA723020ALA641
Revision MK7OA840
Serial YFG7SYUA
Capacity 1863.0 GB
Type Fixed
Bus Type SATA (11)
Rotation speed 7200 RPM
Features SMART
Controller Serial ATA Controller - AHCI at bus 0, device 17, function 0
Volume d:\, 1863.0 GBytes (79.4 percent available)

 

[DarkwinX]

I'm fairly sure this is dependant on if there are MBRs on your drives and multiple boot managers only knowing about one of the drives. From memory it can a game of which MBR gets loaded first based on which drive is enumerated first.

Bcdedit might be able to check each drive for you with a bit of googling.

 

[CDM6421]

I'm fairly sure this is dependant on if there are MBRs on your drives and multiple boot managers only knowing about one of the drives. From memory it can a game of which MBR gets loaded first based on which drive is enumerated first.

Bcdedit might be able to check each drive for you with a bit of googling.

Good call, and I'm familiar with bcdedit.