Web Forms :: Error - Could Not Find File 'C:CHURCHROOF - CRIME Live 150110.xlsx'

I get the following error message:

Could not find file 'C:CHURCHROOF - CRIME live 150110.xlsx'.

When running the following code:

if (FileUpLoad1.HasFile)
{
string serverpath = "\\server1\Temp\ ";
//top.window.close();
string filepath = FileUpLoad1.PostedFile.FileName;
string filename = FileUpLoad1.FileName;
string destination = serverpath + filename;
//File.Delete(destination);
string[] existingFilesArray = System.IO.Directory.GetFiles(serverpath, "*.xlsx");
foreach (string existingFile in existingFilesArray)
{
System.IO.File.Delete(existingFile);
}
File.Copy(filepath, destination);
}

The code looks for a file and uploads the file to another location.

it fails at the last section

It works for me on my machine. but not the users

File.Copy(filepath, destination);

NO matter were the users put the file it fails.