Downgrade Windows 7 x86 to x64/x32?

Hi,

I have an Asus N61Jv Intel Core i5 M430 @ 2.27GHz - Nvidia GeForce GT 325M 1GB (also integrated? Intel HD Graphics) - 8GB RAM

Im having troubles with a couple of games, where I believe they arent chosing the better GPU (325M).
Example;

I scan my PC on CanYouRunIt and this is what I get on Dead Island,



When I go in-game though, it's kinda choppy, lag-like, slower than it should run.

I cant figure out how I force/chose prefered GPU, i've been on Nvidia control panel but im not sure if it's showing every option on there. (strange)



It seems like I have Windows x86.
I read at some post I found through google that someone else had Windows x86 and had same kind of problems (on a different system though).
He wrote:

"I solved the problem by installing windows 7 x64. I had windows 7 x86, and now after installing this windows it works perfect,i can use both them when i want by right-click on a game and select run with graphics processor->nvidia or intel. So at me the problem was solved after installing windows 7 ultimate x64, and x64 drivers from msi.com (my laptop is MSI). Thank you, hope my solution would help others in the future."

So I guess my question is how do I go from Windows 7 to x64?
Or, if anyone has a different solution to my problem?

Im sorry if theres an obvious answer to this, and my question is silly!

Thanks,
Martin

CanYouRunIt appears to already indicate that you have Win7 X64. (X86 is the formal designation for the 32 bit version. It X86 refers to the Intel processor architecture going back to the old 286, while X64 refers to 64 bit instructions.)

You have a notebook with onboard Intel graphics, plus nVidia graphics. I'm not sure how to force the use of the nVidia graphics for games.

Alright, thanks for the quick replies!
System Info it tells me I have;
Microsoft Windows 7 Home Premium 64-bit 7601 Multiprocessor Free Service Pack 1.

Funny thing, straight after I made this post I rightclicked a random game and found run with graphics processor>
where I also found change standard GPU>, I located Dead Island.exe and I could chose which GPU I wanted to use (Nvidia processor with high performance).
Started up Dead Island, runs like it should, alot smoother!

Thanks for your replies guys, appreciate it!