Just received a replacement drive for the one that died a fortnight ago.
The one that died replaced my original C drive as I normally replace C drives after 5/6 years but forgot to do so when upgrading all others (the one being replaced was Feb 09}.
The System image has Boinc on it but with all slots empty (set NNT & completed before imaging).
Do I copy over the slots from ProgramData or all the files in Boinc?

DON'T try to copy separate individual components. The 'slots' are the individual work-spaces for tasks in progress. They are wiped clean at the end of each task, and created / deleted as needed. If you did a clean and orderly shutdown, all the slots would have been empty - well done, that's the best way.

You can put the BOINC data anywhere - it doesn't have to be in ProgramData, or even on the system disk - you have a free choice. But that's where it will be if you didn't make an explicit decision to be different.

My regular instructions, tried and tested over the years, are:

1) Copy the entire BOINC data structure, subfolders and all, from your demised drive / system image, and put it wherever is most convenient. Personally, I've standardised on D:\BOINCdata
2) Download (or recover from the old machine) a full BOINC installer. That's for the program, not the data. Pick any version you're comfortable with.
3) Run the installer. Pause on the second screen, which tells you where everything will be put. Does that match what you just did?
4a) Yes - the locations are right. Continue as usual.
4b) No - I've chose somewhere new. Click the 'Advanced' button at bottom-right. Using the buttons provided, ensure that the second line - the data line - matches where you've already put the data. You can change the program location as well, but it doesn't matter. Free choice.
5) Finish installation as normal.
6) Launch BOINC Manager. All your old projects, tasks, statistics, options, ID numbers, and anything else you care to think of, should be be in their places and ready to rumble. Start her up!
7) Sit down and enjoy a well earned cup of tea. There's nothing else to do.

Okay thanks Richard.
Just have to set NNT & wait for tasks to finish sometime Mon.
No need to reinstall or worry about ID as that is all on the image.