Unable to start Photoshop CS6 - could not open a scratch file because the file is locked (Windows)

Question

When I first installed Adobe Photoshop CS6 I was unable to run Photoshop or Bridge CS6.  Photoshop would give me an error about "could not open a scratch file because the file is locked.  If I ran either of these programs as an administrator they would run without issue, this led me to believe that there was a permission issue somewhere.  After some digging I found out the both Bridge and Photoshop try to create a temp file (similiar to Photoshop Temp2777223910092) on the c:\ drive of the computer.  In my case the user that I was logged in with did not have access to write to the root of the C:\ drive.  Note that you run the program as the administrator and change the scratch disk location as that changes the preference for the administrator user and not the user that you are currently logged in as.
To get around this issue I first had to give the user that I was logged on with write permissions to the root of the C:\ drive.  Next try and run Photoshop, you will get an error another error about the scratch disk and about and invalid or missing setting file.  To correct this you need to have run Photoshop as an administrator, next you can go to Users\Admin\AppData\Roaming\Adobe\Adobe Photoshop CS6\Adobe Photoshop CS6 Settings and copy Adobe Photoshop CS6 Prefs and/or Adobe Photoshop X64 CS6 Prefs to Users\<your logged in username>\AppData\Roaming\Adobe\Adobe Photoshop CS6\Adobe Photoshop CS6 Settings.
Photoshop and bridge should now start up with no issues.
I hope that this can help others out there as this caused me a great deal of frustration when upgrading to CS6.

Answer 1

station_two wrote:
OK, here comes the explanation of what the scratch disk does and why it's optimal to have it on a physically separate internal drive (not partition!) other than your boot drive
I probably shouldn't say anything since it could complicate this thread, but the rules of thumb can be different under special circumstances when SSD is involved.
IF you have a LOT of empty space on your SSD-based system drive, then Photoshop can actually work great with it's scratch setting pointed at the system drive.  This is because a) SSD transfers are much faster than spinning hard drives and b) there's no seek time, so simultaneous transfers to/from scratch and swap files aren't devastating to performance, and you can see a net gain because of the increased I/O throughput over what's possible using a separate spinning drive for scratch.
But if you don't have a huge amount of free space (hundreds of GB) on the system SSD, it's definitely better to use a separate drive, as station_two has said.
Also, up to about a year or so ago, you had to try to severely limit write activity to your SSD drive, since you could actually wear them out by repeated high data write activity.  That's pretty much a non-issue now with the advent of things like the SandForce in-drive controller that does wear-leveling inside the drive.  Modern drives will last 10 years or more in normal typical use, without special consideration.
As it turns out, making a RAID array of SSDs is a great way to boost performance across the board, have bunches of free space, and ensure even the heaviest usage doesn't shorten the drive life.  I have done so, creating a 2 TB system drive C: made from 4 SSDs and Photoshop's swap file (and pretty much everything else) pointed to C:.  This system flies, and I can barely tell when Photoshop and/or Windows "goes virtual" and starts using its scratch/swap files heavily.  I don't even notice Photoshop auto-saves.
Sorry for the SSD diversion.
Back on topic: 
Pretty much everyone who's successfully using a computer - Mac and PC users alike - comes to realize after a while that the task of integrating things on their computers and making everything work falls on THEM, not the developers of applications like Adobe.  Some applications pose unique challenges, but to think you can just throw up your hands and try to make it someone else's problem when something goes wrong simply isn't a viable strategy.  Maybe that's how things should be, but it's not how it is.
For those of you struggling to get Photoshop to run properly, bear in mind that it's on you to get things working.  It works for most folks.  It could be a configuration or setup choice you've made that may need revisiting, or some kind of restorative activity that you need to do, or even something very minor like clearing your Photoshop preferences, but it may well take your learning new things and doing things you didn't think you'd have to do to get back to where you can edit photos.  It's no one's problem but your own.
So let us here on the forum help you - when we say to do something, try it.  We're not here to jerk you around; we're users just like you who have already found the ways to make things work, and we'd like to help you do the same.
-Noel