If connected to sourcecontrol:
Open solution in vs,
select File - Change sourcecontrol - Unbind.
Exit Vs.
Optionally copy files and folders to a new location.
Find all files ending with *.scc (including in subfolders) and delete them.
Delete *.vssscc (mine had only one)
Remove write-protection on files.
Now they are free from Sourcesafe source-control.