I've installed Ubuntu on my 64-bit system using windows installer. What version I might've got??
In the top right hand corner you can get to 'System Settings' and then there should be an option in the control panel like menu at the bottom under system which displays your current version and all that info. It might be called "System Info" or something or "About Me," but there's not a lot of options.
Wubi will install the 64-bit version of Ubuntu if you are running 64-bit windows otherwise it installs 32-bit.
If you have already installed Ubuntu you can check which version you have there are at least two ways to check which has been installed.
To do this the GUI way find "System Settings" by searching in the dash if you use Unity or under the "Applications" > "Systems Tools" menu if you prefer the Gnome Classic desktop. Click on "Details" and with overview selected it will tell you what version you have installed.
To do this the command line way enter
on a 64-bit system you see some thing like
if you see x86_64 you have 64-bit installed, if not its 32-bit.