why am i not being able to write CD's in linux

[leosgohard <leosgohard rediffmail com>]

hi there
i am trying to write the ISO images of RHL 9.0 on CD's  using xCDRoast 
and Nautilus's inbuilt
Cdwriter utility .I am using the genuine 700 blank CD's for this.But 
still both of them end up saying
"not enough space on disk "( need at least 646 MB free ) .
While doing this ...i must mention that
my linux is installed on /dev/hda3   ----> 400 MB free
but iso images were downloaded on  /dev/hda5  ---> 1.2 GB free    
mounted on  /mnt/windows  (its a windows partition added in /etc/fstab 
to mount at boot time)

does it matter how much space i am having free on main linux 
partition..while doing this. ?
( for a kicker.... i was able to write those ISO images on the same CD's 
using Roxio 's Easy CD creator successfully..! after being frustrated 
from linux utils..!)


2) Bob recently answered one of my posts regarding being able to add 
another ext3 partition
as /dev/hda7 to increase disk space available for linux.
i did that ...but despite that second linux partition available 
..whatever rpm or other softwares ..i install ..they dont go on 
/dev/hda7 ...what should i do about it...?
i am just having 200 mb free on my disk now..!  despite the fact that i 
have another 4 GB /dev/hda7  ext3 partitioin available ...it remains 
unused.....what should i do about this whole situation..??

3) what would be the best partitioning scheme ,if i want to do a fresh 
install on  machine with 8 GB space available for linux..
i am aware that if you  mount different   dir's on different disk 
partitioins ..you can handle/avoid the above mentioned problems..(of 
being left with no disk space at all..!!)pretty easily.

please help this newbie..!

3)  one of my friends..(while practising linux commands....) wrote an 
/etc/nologin   as root...( Duh..!!!_ ) and locked himself out of his 
linux box. Is there any way for him to boot into the machine somehow and 
delete that /etc/nologin file to be able to login again.
if not..then he is not ..left with anyother option than to install linux 
again..!!

please help on that front too..!

regards

robin