Why do I have a shared file within Silk Central:- C:\ProgramData\SilkCentral\Working
This working folder is only used for the Demo project that comes with silk central. The "Demodata" folder that you see here is a UNC path that is set up to use this location from a Source Control of the Demoproject.
Therefore, if you are not using the Demo Project or the SCTMWorking directory for UNC Source Control there is no need for it and there would be no issue to disable the share for this reason, to this working folder.
If you are using the UNC profile, you can create a working directory that can be placed anywhere (i.e. on another machine) as long as all SilkCentral Execution Servers and the Application Server has complete access to that shared drive. This is needed because the Execution Servers go to that shared drive to access the relevant files needed to run test definitions such as SilkTest scripts.
On installing a new version of Silk Central, the SCTMWorking folder will be recreated again as it is packaged within the install. Therefore, the share permissions for the SCTMWorking folder would have to be modified again on a new install.