When building the laptop I use, I made (a not uncommon mistake) ... I had Vista installed and as I needed the machine, rather than "risk" an in place upgrade I installed Win7 on an unused extended partition so I could dual boot... So now I am happy with 7 and running low on disk space, which is when I realised I couldn't simply remove the vista partition and merge, because it was the primary partition...
Well that's not so hard, I grabbed a trusted copy of UBCD (Ultimate Boot CD) and using one of the free partition tools... decided to copy my 7 partition over the top of vista and remove the vista partition, for some reason I thought this sounded the simplest solution.
I had the win 7 ISO burned on a disk (for the recovery/repair wizard etc) and expected boot problems, which were duly fixed.
What I had not expected was that Windows would now boot OK but, let me log in OK, but sit for an age "preparing desktop" and then nothing, nada...
Tried running "task man" and couldn't get any exe to run, except "cmd", which is when I realised win7 now thought it was installed on "d".
This is not so uncommon problem and it didn't take long to go through the various solutions, checking diskpart and boot config via the "repair command prompt" when booted into the setup disk.
I eventually figured that I needed to clear the CURRENT MACHINE/SYSTEM/MountedDevices but the mistake I made (and really frustrating) .... As I couldn't get regedit to run in windows I tried (more than once) to clear this when running regedit booted from the repair disk.
This is a mistake - and the penny didn't drop till finding this linked from a 7-forum post.
The point is that you can only make changes when booted into the partition, unless you explicitly open the hive from disk.
