don't think memory is the issue, everything is running on ssds so virtual memory almost as quick and plenty of that available.
Plus the original machine only had 2gb.

Until I've reassembled the machine and checked it does still work - I'm not going to get any nearer I don't think.
In two minds whether to run a chkdsk, it's got a couple hundred bad sectors and probably isn't long for this world, chkdsk could simply move too many bits of software.

I'll see how much memory it pulls on the original machine.