How can I tell if IE 9 is 64 bit?

I have 64 bit machine and Win7 64. I have been trying Firefox Nightly 64 bit and decided to install IE 9 64 bit. I downloaded the 64 bit IE9.
The installer tells me I have a newer IE9 installed therefore it stops.
Under 'About' all I read is version 9.08112.16421 of IE 9.
Have I already installed a 64 bit IE browser I just don't remember? How can I determine if it is 64 bit and if it is not, how can I test drive IE 9 64 bit?

In the browser window click help. If it's the 32 bit version it will say IE9, If it's the 64 bit running it will say IE9 64bit version.

My icons are marked "IE9" and "IE9 64bit"

Thanks to all!
Turns out I have both. The desktop icon opened the 32 bit but I started the 64 bit from its .exe and it runs, verified it with a look at the Help/About. I placed an icon on my taskbar for both.
I've been trying the Firefox Nightly 64 bit, but it is buggy and slow. Not unexpected in a developing version. Mostly I use Chrome and Firefox (32). Today on a whim I clicked the IE9 icon and was pleasantly surprised at the speed and overall appearance. I must be months since I opened it. So then, the thought process, 'how about the 64 bit version?' Just now I opened a couple of sites with 64 and it looks good and is quick.
Thanks again for all the responses.

Note: 64bit is a lot slower than 32bit. It has a different engine.