You don't say what resolution your display is, and some software may require a minimum resolution to work (with 1024x768 being very common). For example, if you're using something like a netbook with 1024x600 pixels resolution, it's not uncommon for some software to refuse to install. The solution is to use a higher resolution external display to install the software in that case.
If your display resolution is sufficient, you may have a problem with the font sizes causing an issue.
I'd check your DPI settings and make sure they're not oversized so that they're causing a problem (reset it to normal temporarily and see if that solves it for you), as it's my understanding that the Canon software wants to make sure some of the text can fit on the screen and font sizes will impact it's ability to install.
See this page on DPI settings in Windows 7 (make your text smaller temporarily and see if the software will install):