What is the best way to Upgrade from Win 7 32bit to 64bit ?

Hi everyone, this is my 1st post so please bear with me on this one.

I had Vista on my PC and upgraded to Win7 32bit via the Retail Upgrade version of Win7 Home Premium (which contains both 32bit &64bit upgrade discs).
I want to now do a clean install to Win7 64bit, can I use the 64bit upgrade disc supplied with the Retail version I already have or do I have to purchase a full version of Win7 64bit ?
Also, is there any foreseeable problems I might encounter on the way ?
Thanks
Graham

Of course you can use that disc. you bought it, its yours. You can use that disc over and over again, and it also has some nice features for repairing a computer. Anyways yes you can use the 64 bit disc in a clean install, just make sure you used the same license key you used on the 32 bit version. Also the both have to be the same product type, for example:
home premium 32bit= home premium 64 bit
ultimate 32 bit = ultimate 64 bit
You can't go from your home premium 32 bit = your new ultimate 64 bit.
Must be the original product type, and product key. Just insert disc, the same key and clean install. Good luck
And there shouldn't be any problems, unfortunately you will lose everything, so backup important data.
If problems do arise, in which they shouldn't then feel free to post back on seven forums.:)

Edit: this may help : Clean Install with a Upgrade Windows 7 Version
*also if you find a windows.old folder on your new version, and it contains files you don't want Then open disk cleanup and you must chose system files select all, and this will rid of it.*

gregrocker said:

When you boot the 64 bit disk it should see the underlying OS on the HD to allow use of Upgrade version key during install. Only if you wipe the HD or use a new HD with no OS does it require leaving the Product Key blank during install then doing the Option 3 workaround in the tutorial in the previous post to Activate.

Retail Win7 can be reinstalled as often as you want in either 32- or 64-bit, even moved to new hardware as long as it also qualifies for Upgrade version.

Didn't know that! Thanks taught me something new as well:)

Thanks for that guys, I shall give it a go, hopefully hassle free !!