So I am following the instructions from bt4install.pdf
And when I get to the last step of fdisk this happens.

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at next reboot.
Syncing disks.
I didn't know what was going on so i rebooted.
root@bt:~# mkswap /dev/sda2
/dev/sda2: Device or resource busy
root@bt:~# swapon /dev/sda2
swapon: /dev/sda2: Device or resource busy
I tried umount /dev/sda2 and it says
mount: /dev/sda2: not mounted

I tried googleing and the wiki.
Thank you for any advice.