I've gotten a ton of questions about the Windows 7 retail pricing stuff, as expected. But the number one question, by far, is an oldie but goodie:

"Can I use a Windows 7 Upgrade version to perform a clean install of the OS?"

This is becoming particularly antsy for people because they want to take advantage of the time-limited Windows 7 presale, which starts tomorrow.

So, what the heck, I asked.

The answer, I'm told, is ... Yes. You can perform a clean install of Windows 7 with the Upgrade media, as you could with Windows Vista.

The second most common questions regards "upgrading" from Windows Vista or XP (32-bit) to a 64-bit version of Windows 7. (You cannot do an in-place upgrade between 32-bit and 64-bit versions of Windows.)

Yes, it's possible. The key is to purchase the Windows 7 Upgrade version electronically (preferably through the presale and directly from Microsoft). If you do so, you're given the choice to download the x64 bits. So if you qualify for a Windows 7 upgrade--i.e. you own Windows XP or Vista--you can buy the Windows 7 Upgrade version of your choice, download the x64 version, burn it to disc, and do a clean install. (Per the previous question.)

Hope this helps.