I could offer some first hand experence with the Ubuntu Wubi Desktop version....
now this was just a couple years ago when it first was released to the public
though I don't think the main things have changed.

It installs as a software with the One Click Windows Installer online with a
windows pc. It does not partition the disk and can be removed as any normal
software on Windows at Add/Remove Programs. It will automatically setup the dual
boot and at start up the options allow to enter either system. I believe the
preferences allow 10 to 30 seconds to choose and which is the default system
that will start up automatically at that time if none chosen.

It will run a tad slow kind of like if run through a usb plug and play drive
which some people have tried.

It is the fully working Ubuntu Desktop with instant connectivity over
broadband/dsl ethernet connection. It is not a demo or 'live distro' - though it
can be used that way without the burning to CD/DVD and install.

I would recommend a regular install and as dual boot since that is apparently
what you want. It will behave much better and stable. Since we are talking IT
Security here I would recommend the full install normally and as well attending
computing security with adding firewall and a real time protection solution such
as ESET. Botnets have been created with Linux and certainly corporate and
home/small business have been targets. As such, I would not operate without real
time solutions and there may be discounted business offerings no doubt. AppArmor
has recently been incorporated into Ubuntu Linux which is a real plus and
unobtrusive - similar to Vista UAC in a way securtity wise. There is encryption
available as well.

My recommendations are not from FUD
http://en.wikipedia.org/wiki/Fear,_uncertainty_and_doubt
or any other uninformed paranoa. Actually I have performed Amatuer Forensics and
as a freelancer IT Security Home/Small Business. You Do Not want to take
unneccesary unrecommended chances in security I think goes without saying for
your position. As well I am a degreed accountant and need not mention client
security in all matters. Further yourself in database protections as well I
would recommend.