Hmmm, putting the mdb in root of a drive is going to give you a whole heap of hassle, as Jet needs certain things set at folder level.
I would recommend moving the mdb file to its own folder - for example c:\stock - and adjusting where SCM and PCTill look for it ("c:\program files\stock\stock.exe" /configuredb:yes)
The permissions on this folder are probably best initially set to Everyone Full Control.
Are you running the latest Jet and SP (Jet4 with SP8), and which OS are you running.
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