By "multi-booting", I mean choosing from a range of Operating Systems (OSs) at boot time, without having to insert boot disks. Here's a rundown of what works with what, with respect to Microsoft OSs...
Visibility:
- cannot see Long File Names
- cannot see FAT32 or NTFS
- older than 4.0, 32M volume size limits may apply
- 8G barrier issues
Footprint:
- PBR, certain files in root:
- IO.SYS, MSDOS.SYS, D??SPACE.*,
WinBoot.sys
- Config.sys, Autoexec.bat
- relocatable DOS subtree
- relocatable Temp subtree (MS-DOS 6+)
Share boot partition with:
- Win95 (not SR2.x), Win98 via "Previous
version of MS-DOS"
- any DOS mode or Win9x if footprint swapping is
managed
- any NT if NT doesn't interpret Config.sys or Autoexec.bat
- in all cases, C: must be FAT16
Risks:
- loss of Long File Names (no protection against low-level
disk access)
- variances in drive letter allocation
- no other "normal" auto-changing risks
- if careful with above, no need to hide other hard drive
volumes
- safe to run on arbitrary hardware (no Plug-n-Play)
- safe to run on at-risk hard drive; some commands may spawn
temp
Recommend:
- Win9x DOS mode instead, unless specifically need
MS-DOS version
- use same partition if caveats observed
- else use alternate primary partition
- can run off 1.44M or CDR instead
Visibility:
- cannot see Long File Names
- pre-SR2.x Win95 cannot see FAT32
- cannot see NTFS
- 137G barrier issues
Footprint:
- PBR, certain files in root:
- IO.SYS, MSDOS.SYS, D??SPACE.*,
WinBoot.sys
- Config.sys, Autoexec.bat,
Winboot.ini
- relocatable "Windows" subtree
- relocatable Temp subtree
Share boot partition with:
- MS-DOS via "Previous version of MS-DOS" as long as:
- the Win9x DOS mode is not
Win95 SR2.x (fails to return)
- C: is FAT16
- you accept the risks to LFNs
involved
- any DOS mode or Win9x if footprint swapping is
managed
- difficulties with WinME that can be
overcome
- any NT if NT doesn't interpret Config.sys or Autoexec.bat
- in all cases, C: must be FATxx (pre-SR2.x
Win95 requires FAT16)
Risks:
- loss of Long File Names (but protects against low-level
disk access)
- variances in drive letter allocation
- no other "normal" auto-changing risks
- if careful with above, no need to hide other hard drive
volumes
- safe to run on arbitrary hardware (no Plug-n-Play)
- safe to run on at-risk hard drive; some commands may spawn
temp
Recommend:
- use same partition if caveats observed
- else use alternate primary partition
- can run off 1.44M or CDR instead
Visibility:
- pre-SR2.x Win95 cannot see FAT32
- cannot see NTFS
- 137G barrier issues
Footprint:
- PBR, certain files in root:
- IO.SYS, MSDOS.SYS, D??SPACE.*,
WinBoot.sys
- Config.sys, Autoexec.bat,
Winboot.ini
- relocatable "Windows" subtree
- non-relocatable Recycled directory
- non-relocatable "Program Files" subtree
Share boot partition with:
- MS-DOS via "Previous version of MS-DOS" as long as:
- the Win9x DOS mode is not
Win95 SR2.x (fails to return)
- C: is FAT16
- you accept the risks to LFNs
involved
- any DOS mode if footprint swapping is managed
- any Win9x GUI or NT requires intense footprint
swapping management!
- more practical to locate bulk of OS
on a different hard drive volume
- in all cases, C: must be FATxx (pre-SR2.x
Win95 requires FAT16)
Risks:
- subtle Long File Name issues for multiple similar-8.3 names
in NT
- sharing the same "Program Files" even if re-pathed in
registry
- variances in drive letter allocation
- no other "normal" auto-changing risks
- if careful with above, no need to hide other hard drive
volumes
- UNsafe to run on arbitrary hardware
- Plug-n-Play detection of devices
- OS may make changes to system-level
PnP NVRAM / ESCD
- UNsafe to run on at-risk hard drive; always writes swap,
temp etc.
- UNsafe to run with ?infected hard drive:
- \Autorun.inf processing unless
disabled
- Desktop.ini processing unless "View
As Web Page" suppressed
- difficult to keep "View As Web
Page" suppressed in Win98
- may be additional risks from
persistent handlers
Recommend:
- install OS to logical volume; still needs to boot from C:
- else use alternate primary partition
- Win95/98 includes DOS
mode as its mOS; ensure this works
Visibility:
- cannot see NTFS
- 137G barrier issues
Footprint:
- PBR, certain files in root:
- IO.SYS, MSDOS.SYS, D??SPACE.*,
WinBoot.sys
- Config.sys, Autoexec.bat,
Winboot.ini
- relocatable "Windows" subtree
- non-relocatable Recycled directory
- non-relocatable "Program Files" subtree
- non-relocatable \_Restore on all visible hard drive
volumes!
Share boot partition with:
- any DOS mode if footprint swapping is managed; but
see details
- any Win9x GUI or NT requires intense footprint
swapping management!
- more practical to locate bulk of OS
on a different hard drive volume
- in all cases, C: must be FATxx
- NB: additional issues relating to startup files,
SR and SFP
Risks:
- subtle Long File Name issues for multiple similar-8.3 names
in NT
- sharing the same "Program Files" even if re-pathed in
registry
- variances in drive letter allocation
- auto-write risks posed by SR
and SFP
- because of the above, unsuitable for use for drop-in
hard drives!
- UNsafe to run on arbitrary hardware
- Plug-n-Play detection of devices
- OS may make changes to system-level
PnP NVRAM / ESCD
- UNsafe to run on at-risk hard drive; always writes swap,
temp etc.
- UNsafe to run with ?infected hard drive:
- \Autorun.inf processing unless
disabled
- Desktop.ini processing
- may be additional risks from
persistent handlers
Recommend:
- install OS to logical volume; still needs to boot from C:
- else use alternate primary partition
- make sure you have a working
maintenance OS
- avoid dropping in sick/infected hard drives from other PCs
Visibility:
- may have NTFS version issues with different NT versions
- older NT versions may have 137G barrier issues
Footprint:
- PBR, certain files in root:
- NTLDR, Boot.ini, some others (but
no overlap with DOS/9x)
- Config.sys and Autoexec.bat if
set/left to interpret these
- relocatable "Windows" subtree
- non-relocatable "Program Files" subtree
- non-relocatable Recycled directory
- non-relocatable "Documents and Settings" subtree
- non-relocatable "System Volume Info" on all visible hard
drive volumes
Share boot partition with:
- same-version Recovery Console
- any DOS mode if the NT ignores Config.sys and Autoexec.bat
- any Win9x GUI or NT requires intense footprint
swapping management!
- more practical to locate bulk of OS
on a different hard drive volume
- in all cases, C: must be visible to other OSs
- can use inbuilt NTLDR / Boot.ini system to access other OSs
Risks:
- subtle Long File Name issues for multiple similar-8.3 names
in Win9x
- sharing the same "Program Files" even if re-pathed in
registry
- variances in drive letter allocation
- auto-write risks posed by SR,
SFP, thumbnails
- may "auto-upgrade" NTFS version of visible older NT volumes
- may be incompatible with newer NTFS versions
- may "auto-fix" bad clusters in NTFS volumes
- reports of changes made to registries of alternate NT
installations
- because of the above, unsuitable for use for drop-in
hard drives!
- UNsafe to run on arbitrary hardware
- NT 3.x; crashes when
inappropriate hardware drivers used
- NT 4.0 and later; Plug-n-Play
detection of devices
- NT 4.0 and later may change
system-level PnP NVRAM / ESCD
- UNsafe to run on at-risk hard drive; always writes swap,
temp etc.
Recommend:
- install OS to logical volume; still needs to boot from C:
- else use alternate primary partition
- hide alternate NT installation volumes when these are
inactive
- make sure you have a working
maintenance OS
- avoid dropping in sick/infected hard drives from other PCs
- careful dropping in NTFS hard drives from older or newer NT
(C) Chris Quirke, all rights reserved - April 2004