how to change window7 from 64bit to 32bit

you buy the Windows 7 as retail, with the two discs?
no
Did it come installed on your computer?
yes

Well, it looks like your stuck with Windows 7 x64 version.

Your product key will work with an x86 version though. Maybe you could find a friend who has the x86 disc you could borrow and install it.

Also changing from x64 to x86 system you will have to do a clean install and reformat your hard drive too. That's the only way it can be done.

i am making a desktop application where i am using m.s.access as a oledb 4.0 provider with c#.
but there is a error my local system doesnot resister oledb 4.0 provider

Last night, I tried my product key to give me a clean version of Windows 7 (my key is not on the desktop casing), so I used Belarc Advisor and Jelly Bean Key Finder, they both report the same key, but my regular version of Windows 7 (Home Premium) would not activate with the key. I had to resort to the recovery partition to reinstall, and guess what? The programs still both show the same key. Then, I reentered my Anytime Upgrade key, and Pro was reinstalled, too. So, the regular versions of Windows 7 (the ones from Digital River) won't always activate with the OEM key. I read somewhere that many of the large OEM's use the same "master key" for activation for many installs, saving them (and us) lots of money. It was in the Jelly Bean Key finder that I read this.

please I want more explain I donot understand how make 32 bit if re-install[/QUOTE]

So... If i have window 7 64bit business, then i don't have selection of installing either 32bit or 64bit?? (I cannot find the selection if there is)

Again,It is true that

64bit win7 business dvd can only install 64bit window7 business
and 32bit win7 business dvd can only install 32bit window7 business

There is no difference needed in the BIOS (F10) for 32 or 64 bit.

To switch to 32-bit you must have the 32-bit install discs (or a downloaded copy). You should back up all your data. Then you must do a complete reinstall of Windows 7 including new 32-bit "drivers". You must reinstall all your programs. and then restore your data.

Any RAM > 3.25GB will no longer be available because 32-bits cannot read beyond there (cannot address the RAM above 3.25GB).