install windows7 64 bits using license of 32 bits?

I bought Windows7 - 32 bits. Can I install 64 bits using the same license number I had for 32 bits?
Thanks for anyone helping me.

Yes, so long as the x64 edition is acquired legally.

If you bought the retail version or upgrade version then you should have two discs in the package. One for x86 and the other for x64.

One product key works for either version, it's just one install per key though.

Thanks to Core and Nibiru.

My license is OEM for 32 bits only.I desire to install in 64 bits but I don't want to purchase new license and just use the existing license number for 32 bits.

Presently I have a computer running 64 bit Windows Vista. Are there any risks installing 32 bit windows 7? I wonder, if one installs the 32 bit version can one subsequently upgrade to 64 bit on the same license?

Yes you can, just grab a retail version & it will have 2 DVD's in it, one for 32bit and the other for 64. If you go 32bit, you have to reinstall everything to move to 64bit so it's not an 'upgrade' in that way

And one product key for both versions.

Use the Bing search engine and you'll be able to find these downloads of the ISO image files. Copy and paste the X15-*****.iso into Bing and search from there.

32 bit Home Premium: X15-65732.iso
64 bit Home Premium: X15-65733.iso
32 bit Professional: X15-65804.iso
64 bit professional: X15-65805.iso

The search will then produce a download link that looks like this:

http://msft-dnl.digitalrivercontent..../X15-65805.iso

My two cents:
Install Win7 64, we will be forced there in the near future so you might as well get your support train started as well as your hardware upgrades. 64 bit hardware and the Mac 64 bit OS has been around for a while now so MS has to at least match it.

...
I have window 7 64bit business... i want to change to 32bit business..
my window 7 is OEM version
so.. if i can find a window 7 32bit business OEM version DVD, then i can use the dvd to install 32bit window but using my 64bit cd key?