Access Denied While Using System.Diagnostics.Process

I am trying to use the unmanaged ImageMagick library in my ASP.NET application from the command line using System.Diagnostics.Process. Basically, users will upload an .eps file to the site, and then I will run the command line command to convert it into .jpg. This is the code I'm using to try and run the command:

Dim proc As New System.Diagnostics.Process
proc.StartInfo.RedirectStandardOutput = True
proc.StartInfo.RedirectStandardError = True
proc.StartInfo.FileName = "C:Program Files (x86)ImageMagick-6.6.1-Q16convert.exe"
proc.StartInfo.UseShellExecute = False
proc.StartInfo.Arguments = String.Format("{0} {1}", Server.MapPath("~/logo/test.eps"), _
Server.MapPath("~/certificates/temp/test-1234.jpg"))
proc.StartInfo.CreateNoWindow = True
proc.Start()

I am able to run this code just fine on our development Win 2k3 server, but not on our production Win 2k3 Server. I get the error "System.ComponentModel.Win32Exception: Access is denied". The main between the two servers is that the production is 64-bit and runs Plesk to manage multiple domains. I've tried adding rights asp.net user to the ImageMagick directory. The PS Admin says that in the case of Plesk, it's the same account that I use to access the site in VS using FPE. Does anyone know what I might do in order to allow this process to run on my production server?