Transfer MSDNA license

I have 2 licenses for windows 7 from MSDNA (one 32bit and one 64bit).
I installed the 32bit at my main PC and the 64bit at my secondary pc. I want to upgrade my RAM to 4GB on my main pc and therefore i should change the OS to 64bit.
The problem is that win7 is activated on both machines and my MSDNA account is deleted (I recently got my degree and I'm no longer a student). I have the license keys for both my installations but...

If I format both my PCs and reinstall windows on them (the way I want) will everything be ok?
If I don't format, is my license still valid, or should I buy fresh copies?

Your license for your 32-bit install will work with 64-bit version. They are interchangeable as long as you install the same SKU the key is for. You 32-bit Windows 7 Professional key will work with 64-bit Windows 7 Professional. So as long as you have 2 keys for Windows 7 you can install on 2 computers and 32-bit or 64-bit doesn't matter as long as it is the same version. You download rights have expired from your MSDN account, but the keys are good forever.

Thank you for the reply (and moving the post).
So I can format both my PCs and reinstall the other PC's version. Sorry for repeating myself, I just want to make sure that my license will be valid if it is installed on another PC (since I have already activated it once).

Also to modify the question a bit,
Can I (since I have 2 keys) install on both my PCs the 64bit version of windows?
one key is for the 32bit and one for the 64bit (both professional)

Yes you can install 64-bit on both machines. Even though the key came with 32-bit disc it will work with 64-bit Windows 7. So you can install Windows 7 Professional x64 on both machines since you have 2 keys. Your 32 bit key will work with your 64-bit disc.

...and if you have key trouble, call the number on the card that has your key on it, they will help you.