Missing VST's warning when attempting to load old projects

I am in the process of going through some older projects and either just backing them up or reworking them.
The problem I am currently facing is that some of the projects load but with a warning that some of the vst's i've used are missing. I've rescanned the vst folders and pretty much everything is there that is required, however I cannot work out how to replace them in the synth rack whilst preserving the preset state of the sounds that I had originally used.
I know I should have saved individual presets, but a lot of those projects were older ones where I wasn't so savvy.
How would I go about loading these projects up and getting them to recognise the vsts without all the fiddling?
Or is all lost?

Cheers.