head -1 somefile > sometempfile
set /p var=<sometempfile
tail +2 somefile > sometempfile
mv -f sometempfile somefile
I could have also used sed instead of head & tail, it would have been something like:
sed -n "1,1p" somefile (instead of head -1)
sed "1,1d" somefile > somotherfile (instead of tail +2)
The temporary file is required in XP for setting the variable value, cause XP batch files don't allow setting the variable to the output of another command, which is kind of lame!