The rationale is as follows.
We now have the 1st-stage ReactOS setup running with its own registry SYSTEM hive,
similarly to regular ROS running instances (livecd, regular installation...).
The ReactOS-specific SetInstallPathValue() hack, introduced in a76689e9 (r3794)
and 5f973ce0 (r3795), is removed. This hack told the kernel that, during the setup,
it had to "switch" the used registry hives and instead use the ones of the ROS
installation being prepared.
This was really hackish because this means, mixing between registry settings used only
for the setup running instance, that could use different registry settings
than the ones that should be set for the ROS installation being actually performed.
Also, note that in the case of a 1st-stage GUI setup, consisting in running the
LiveCD + the GUI setup program, this situation would be untenable. Note also that
for people willing to use the Setup*** functions exported by setupapi.dll to parse
the registry INF files to initialize the registry of the ROS installation being
prepared, this would be impossible either.
Hence the need to have offline registry modification functionality.
svn path=/branches/setup_improvements/; revision=74766
bbb04c470a