Systems Management

I am an SCCM noob and I'm attempting to push an updated HOSTS file and a MacroMedia Flash configuration file to the appropriate folders under the Windows\System32 directory, but I'm getting "Access Denied" errors and can't seem to figure out what I'm doing wrong. My clients are a mix of 32-bit XP and Vista, and Win7 (32 & 64 bit).

The destinations are:
1) %windir%\System32\Macromed\Flash\mms.cfg (this folder exists on the clients, most do not have the actual file...)
2) %windir%\System32\drivers\etc\hosts

Here's the command-line I'm using:
xcopy /y %~dp0mms.cfg %windir%\System32\Macromed\Flash\
xcopy /y %~dp0hosts %windir%\System32\drivers\etc\

I have the files to be copied and the batch files in the same directory for each package. I have selected "Run with administrative rights" and "Whether or not a user is logged on" in the package, and "Download content from distribution point and run locally" in the Advertisement. My understanding is that the SCCM client runs as the "Local System" account on the client and should have full access to these folders and files.

I'm sure it is something fairly simple that I'm missing, but right now I'm just not getting it.
Thank you for your help.
-Rob