Server Error in '/' Application

We have a .net application that runs a powerpoint executible and ends the process. This works fine, but when it starts it is supposed to determine if the process is already running and if it is, kill it. It will only kill it if it started the process, but fails with this error if it tries to kill a process that was previously running:

Access is denied
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ComponentModel.Win32Exception: Access is denied

Source Error:

Line 741: For Each pItem In pCollection
Line 742: 'Try
Line 743: pItem.Kill()
Line 744: 'Catch
Line 745: 'End Try


Source File: D:\WebApps\PDIV0R12\Proj\ProRpt1.aspx.vb Line: 743

Stack Trace:

[Win32Exception (0x80004005): Access is denied]
System.Diagnostics.Process.Kill() +107
_Default.KillGraph() in D:\WebApps\PDIV0R12\Proj\ProRpt1.aspx.vb:743
_Default.AddFooterGraph(Presentation objPres, Slide objSlide, Int32 LeftMargin, Int32 Top, Int32 TotalWidth, Int32 TotalHeightPer) in D:\WebApps\PDIV0R12\Proj\ProRpt1.aspx.vb:872
_Default.CreateFile() in D:\WebApps\PDIV0R12\Proj\ProRpt1.aspx.vb:322
_Default.Button3_Click(Object sender, EventArgs e) in D:\WebApps\PDIV0R12\Proj\ProRpt1.aspx.vb:968
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
System.Web.UI.WebControls.Button.RaisePostBackEven t(String eventArgument) +107
System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102

We can't figure out where the access denied is coming from. Any help would be greatly appreciated.

Thank You

Kristine