For those, like me, that get an error message with HMRC's RTI program on a new computer (and get no help from HMRC) then this is the solution from Phil Shepton:
Solved this one on Win 10 64bit saying I haven't got permission. This was a new laptop.
You do not need to alter any permissions at all or mess with security in any way. This is a totally safe and simple process. It does not alter windows files or settings in any way.
Install the RTI as usual and run it, when it says you don't have permission to access database just close RTI.
Open windows explorer, at the top go to 'view' and tick 'hidden items' and 'file extensions'
1) Get a current backup which is in zip format and open it in windows explorer. You will see three files.
2) Highlight and Copy these three files. (no need to extract them first, just copy them)
3) Go to c:\users\**your username**\appdata\roaming\HMRC\payetools-rti folder
4) delete the files in here including the sqlite3.db file which is causing the problem
5) paste the files from your backup in this folder (includes a new sqlite3.db file)
RTI will now open
Open RTI Basic tools and your current data will load.
Hope it helps, it took an hour to figure this way of doing it, , but at least it works.