Windows 7 - Dual boot 32 and 64 without hiding?

I have a 1TB HD and a 500 GB one. The first one dual-boots Windows 7/32 and Ubuntu 10. The second one, I use for storage/backup only. The first one has perhaps 300 GB free and the second one, about 250.

I was given a program that will run only in 64 bit Windows 7. According to my research, there's no safe way to upgrade from Windows 7/32 to Windows 7/64 and I'm not eager to spend days reinstalling software and configurations.

So, I want to install Windows 7/64 in the second hard disk and add it as an entry to my GRUB.

In my past experience, 2 windows installs in the same PC had to be kept from each other by having a bootloader that would hide the partition that was not chosen at the start. Otherwise, errors would ensue because of duplicate system files.

Does anyone know if the same would happen by having two Windows 7 installs in the same system, or if it's already fixed? I would like to avoid keeping a good chunk of gigabytes blocked.

Thanks.

First partitions arent hidden.

Second a win 7 32bit and win 7 64bit and a linux flavor can co-exist quite nicely. Im doing it now.

What do you mean by ".. a good chenk of gigabytes blocked"?

What I meant was: If I have to "hide" a Windows 7 partition and all it contains whenever I use the other one, I'm blocking good gigabytes either by being unable to use them or by having to keep two copies of the same information in either partition.

That's why I want to know if I can have another Windows 7 install in another partition that's fully visible to the one that's got the active OS. I once installed XP and XP MCE (different languages) in two partitions and upon finding "system files" out of place, the whole system went nuts trying to "fix" it.
Partition Magic's Boot Magic (form a few years ago) was a bootloader that woudl automatically hide the other OS's partition along with its data, thus preventing this kind of mess up.

One solution may be to create a data partition for your Windows 7 installs then link your User folders in both OS's to that data. User Folders - Change Default Location

You can also keep your data on one Windows 7 installation and link the other Windows 7's User folders to the ones in the first Windows 7 installation.

There are no worries any longer about multi-boots messing with each other at all similar to what you experienced in XPired.

As I don't use Ubuntu I don't know if the same data can be linked into Ubuntu but know that it can for Windows 7 multi-boots.

Just out of curiosity, why waste two licenses of Windows 7 by dual-booting the same thing on the same system? There's very little to no reason to need both Windows 7 x86 and Windows 7 x64 on the same system, and it would also require two separate licenses.