I've had that situation (system installs with system drive = G: or whatever)
happen to me a couple of times.
The really *pathetic* things about it is that:
a) it's easy enough to happen by 'accident'
b) you SHOULD be able to do it intentionally if you WANT to,
c) Windows itself seems to work that way (at first glance)
d) Tons of 3rd party programs seem to be so poorly written that they *BREAK*
during installation (or use) if there's no (C drive or if (C:\Windows) or similar isn't %WINDIR%; it's like they freaking HARDCODED ("C:\Windows") into their program installers / code. WTF?! There are the system environment variables like %WINDIR% and %SYSTEMROOT% which are there for a REASON, and they've been documented by Microsoft since like what, Win3.1 days?!
e) And WTF is it anyway about MANY 3rd party software that FORCES you to install all or part of it to C:\Windows, C:\Program Files, or whatever, instead of being happy to install on say Q:\Installs\SomeProgramName?! Do they have to SPEW their CR*P all over my system directories instead of being happy to install their files all in one managable, neat, confined folder and its subdirectories?! I'd LIKE to have basically a READ ONLY %WINDIR% / C:; place %TMP% and %TEMP% e.t. a.l. somewhere ELSE, place Program installs like on Q:\Installs\ProgramName, place all the user profiles on somewhere like H:\Users\Username\..., etc. Why is that asking SOO much, it's SUPPOSED to work...?
f) And WTF is wrong with people that write these programs that spew billions of basically private configuration settings into your SYSTEM registry for no particularly good reason. Would it freaking kill application developers to actually write their program's private configuration settings to files / databases WITHIN the directory tree the program installs in? Would it kill the app developers to NOT hardcode absolute PATHNAMES of C:\Windows\whatever, D:\Install\MySoftware\etc. into their registry / configuration files? So if I install a new hard disc. and programs that were originally "installed" to "D:\somewhere" will actually KEEP WORKING if the partition / drive changes moves that location to "E:\somewhere"?! Or if I install the PROGRAM on (D, have my OS on (C but then dual-boot into another OS variant which ALSO has access to the same (D (i.e. the program is in the SAME place), but the OS as (C is now a different version ... would it be asking so much for the programs to actually WORK if I launch them rather than have to REINSTALL them even though they're already INSTALLED onto the same (D place or whatever?
Oy. Windows sucks; thank GNU for Linux where mounts / links / program installs / path searches are actually usually fairly flexible.