Wubi paranoid friendly?

[Richard Owlett]

I date from the era of vacuum tubes and 026's.
Though I've programed, I'm a user not a programmer.
I am a Windows(tm) user who wishes to be a *nix user.

I wish to try Ubuntu.

Full install OBVIOUSLY *NOT* acceptable ;/

Dual boot *NOT* acceptable as it requires repartitioning my hard 
drive. I've had bad experiences with repartitioning.

I've already gone the "live" CD/USB route which proves that my 
hardware is minimally compliant

!!! *BUT* !!!

I'm looking for something indistinguishable from a full install, 
think equivalent of "Turing Test" ;/

Basic question is:
"How does Wubi mess with my hard drive?"

I've searched multiple Wubi related pages without an adequate answer.