[NPMUG] Time Machine

[Dadditude]

I currently have the following Setup on my Mac Mini:

Internal Drive: 160GB (~30GB for Windows XP; ~130GB for Mac OS X)
External Drive: 500GB

I am wanting to set up the external drive for storage and backups, but  
am unsure of how I should set it up. I want to have as much available  
for storage as possible while still being able to backup with time  
machine. Not sure if I should partition the external drive or not, and  
if so, what size partitions I need to set up.

Any and all advice will be appreciated. Thanks in advance.

-- 
"We do not quit playing because we grow old; we grow old because we  
quit playing." - Oliver Wendell Holmes