| depending on what you are trying to do:
df |sed '1d'|awk '{if ($5 > 90) print $5,$6}'|sort -r
99% /harddisk/C
96% /harddisk/E
df |sed '1d'|awk '{if ($5 > 90) print $6}'|sort -r
/harddisk/C
/harddisk/E
or unsorted:
df |sed '1d'|awk '{if ($5 > 90) print $5,$6}'
96% /harddisk/E
99% /harddisk/C
/edit: df |sed '1d'| awk '$5 > 90 {print $5,$6}'
also works .. |