Can i possibly do this? If not, what r my alternatives

[Kapil Khanna <boomkap usa net>]

I recently installed Redhat on an old P2 laptop. It works like a champ and i
am extremely pleased. However the laptop only comes with 2.5 GB of hard drive
space. Using the system over the last couple of weeks has the drive at 60% of
its capacity. Thats making me anxious that someday i will have to deal with
space issues.
I was successfully able to map a Windows file system from another machine on
my network via Samba on /mnt. 
I have always wondered if i can mount this additional windows file system on /
(root) rather than a sub directory of /. That way i can add virtual hard drive
space to that Linux box. In fact i tried doing this once but was unsuccessful
with a message saying the device/resource was busy.
Any ideas on how i can get around this problem? I have thought about symblins
from the linux file system directories to the samba share, what other options
can i explore? If i install an external hard drive will that add space to my /
(root) file system? 
A df on my machine reveals the following:
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hda2              2885216   1622088   1116568  60% /
/dev/hda1                50723      5967     42137  13% /boot
none                     47188         0     47188   0% /dev/shm