I agree with both you & Oberwald. Putting the system & applications on the C drive with your own user folders on a D drive has benefits.
I did this after much agonising but now wish I had done it as soon as I bought the PC. This setup allow me to make a system image onto an external HDD that is only about 30GB & that only takes about 20 minutes to complete [previously, making a system image
of a drive that contained the system, all applications & all the datafiles was impracticable as it was 200-300GB]. I now make an image each week & keep the last few ready for any major problems; I have restored a few times without any problems [this also
takes about 20 minutes]. Unlike, for example, Acronis system images, the Windows Backup System Image is restored just to the partition it came from so the D drive datafiles are not disrupted.
You can manage the system images easily. They are always made in a WindowsImageBackup folder on the root of the external HDD. Just create a folder called something like ImageLibrary then subfolders with the dates & just move the whole image folder into
it. You end up with J:\ImageLibrary\20120702\WindowsImageBackup, J:\ImageLibrary\20120629\WindowsImageBackup and so on. When you want to restore from an image, just move it back to the root of the external HDD, J:\WindowsImageBackup, as it is only in that
location that Windows can restore from it.
I also create fairly conventional datafile backups using 3rd party tools but also create a mirror image of my user folders on my external HDDs using the Win7 utility RoboCopy. I always do this before restoring the system partition just as a precaution but
have never had any problems with restoration anyway.
To put the user folders onto the D drive is easy. Create a D:\Documents folder then go to C:\Users\YourUserName then right-click on each of the user folders & use the location tab to put them within D:\Documents. I also use D:\SystemSettings for things
like the Favorites folder & D:\Desktop as I prefer to have them clearly separate from my own filing system. You will need to set security permissions on the top-level D drive folders to keep them private.
While you are at it, and I mention this because you are clearly taking system reliability seriously, make a spare admin account & create "password reset disks" for each account. This will protect you from user profile corruption.
Search this forum for "admin password" & you'll see the problems some people have. The idea is that if the first admin profile is corrupted, you'll be able to get in with full permissions on the second admin account so you can sort things out.
I write down my installation procedures & registration details in an Excel file that is then both a permanent record & a guide for use during most of the reinstallation procedure.