If your PC is a desktop that has a spare 5 1/4" expansion bay,
the least complex way (although it may involve the most physical
work and expense) is to use a "mobile rack" or "drive caddy".
Such a device enables you to easily swap hard drives when you
want to swap OSes - you just have a operating system on each
of 2 hard drive trays that you choose between. Kingwin makes
an extensive line of mobile racks for both IDE ("PATA") and
SATA hard drives:
http://kingwin.com/mobileracks.asp
For PATA HDs, I like the model with (the very effective) 80mm
fan in the bottom of the removable tray:
http://kingwin.com/product_pages/kf812tbk.asp
Search Google using "Kingwin" and the model no. for prices.
They usually go for around $25 for the assembly, maybe $17
for extra trays. Internally, these mobile racks plug into HD
controller ports just like any internal HD. If you need longer
cables (or shorter cables) to fit inside the PC's case, Silicon Valley
Compucycle sells an extensive line of "round" cables for
PATA drives:
http://www.svc.com/ide-floppy-cable.html and
various lengths of SATA cables for
SATA drives:
http://www.svc.com/sata-cable.html .
Another more difficult, but very effective, procedure is to use
an SPDT micro toggle switch that controls the power for each of
2 internal HDs - one OS on each HD. (In the case of PATA HDs,
this works best if each HD is at the end position of its IDE cable.)
By setting the switches before applying power to the PC, you can
control which HDs are seen by the BIOS and thus which HD controls
booting. The running OS has no access to the files in the other HD,
and no conflict exists in regards to restore points. I have such
microswitches mounted in the 1/4" i.d. ventillation holes under the
plastic fascia of my desktop, and by reaching with a bent paper
clip, I can control which HD(s) get(s) power.
You could also install each OS independently on separate HDs,
i.e. with only the HD connected that will receive the installed OS,
and by using the BIOS just after startup, you could set which HD
would have boot control. That would control which OS gets booted,
but since the running OS would be able so see the files of the other
OS, you would still have to contend with the restore point conflict.
But the eventual removal of the unwanted OS would be trivially easy
for all these methods - just remove the HD containing the unwanted
OS.
*TimDaniels*