I tried running the included chkdsk that appears on the RAMDRIVE on the C: drive on a machine yesterday. While the command itself works fine, using the -r and/or -f switches gives you an error and asks you if you want to unmount the drive. Any idea why this is or does the PE just not support those functions?

if you are trying to run chkdsk on a drive from PE you need to be sure not to have a folder open on the drive you are running chkdsk from and be sure to use the correct drive letter for the drive you want to check.