Um...
/dev/sda1 is one of your partitions... You don't want to clear data on the partition that you need...
Type "df -h"
Mine looks like this
[root@ns1 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 215G 44G 161G 22% /
/dev/sdb1 916G 503G 368G 58% /backups
/dev/sda1 122M 21M 95M 19% /boot
[root@ns1 ~]#
Now my partitions are setup very simple and if I was looking for things to clear out I would be looking for old logs and unneeded backup files. Pick up a good unix book or play around on a test box with partition sizes.