I don't understand what you mean by 'Not a 32-bit application'
. There have been nothing but 32-bit mIRCs since v6.0.
Is the installation freezing at a file called 'urls.ini'? If it is, you might want to take a look at this thread
. Older antiviruses may interfere with the installation and think urls.ini is a virus.
It's a good policy to always close other running applications when installing mIRC, including those in the tray and taskbar. This includes (temporarily) antiviruses that may have 'auto protect' features enabled. After installation reboot so those programs can start up again.
What is the exact error you're gettng?