is the path i have mapped work only on my local machine?

hi,
i have the following code. what i have tried to do is map a path which points to my R:/ - the value 'R:\' is stored in my web.config file. this drive is on my server.
what i then do is pass the file name and play in an embedded media player in the web browser. when browse the website everything works fine. however, when i browse the website on another PC, i get an error saying it cannot access the file. is this because the second PC i tried the wesbite on doesnt have an R:\ drive?
i wouldnt have thought this was a problem though. is what i am doing wrong? does anyone know why i cant access the file on that drive?
fileName = ConfigurationManager.AppSettings["MappedDrive"] + fileName; 
thank you very much
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