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I'm upgrading a computer. Among other things it now has 8GB of memory instead of 2. Currently it runs Windows Seven 32bits, but to support that much memory I need to install the 64bits version.

So here comes the question:

I have only one hard drive with no free partitions so I'd like to just install Windows Seven 64 bits over the 32 bits version already installed, without loosing the data, is that possible?

P.S. : I used to do that with older versions of windows, I ended up with a fresh intall, but the data is still on the disk

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the other question is about vista, there is no vista in my question. And I don't want to make an upgrade (as it's not possible) I want to install on top of the old installation. It used to be possible with older versions of windows. – foke Dec 27 '11 at 15:12

You can use the Upgrade option during Windows 7 installation, which preserves your files, settings, and programs, only if you're currently running a 32-bit version of Windows Vista and you want to upgrade to the 32-bit version of Windows 7. Similarly, if you are running a 64-bit version of Windows Vista, you can only perform an upgrade to a 64-bit version of Windows 7. For more information, go to Upgrading to Windows 7: frequently asked questions on the Windows website.

If you want to move from a 32-bit version of Windows to a 64-bit version of Windows 7 or vice versa, you'll need to back up your files and choose the Custom option during Windows 7 installation. Then, you'll need to restore your files and reinstall your programs. For more information about performing a custom installation, see Installing and reinstalling Windows 7‍.


In short, No you cannot do this. You will need to back up your files (or create a partition with your one HDD and back up the files to the other partition).

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This is incorrect. If you choose Custom, Setup will move all your old files to Windows.old. Only if you explicitly tell Setup to format your drive do you lose your data. So the short answer is "Yes, you can do this, but follow these steps. – surfasb Dec 28 '11 at 0:12
I know that is true on upgrades from like WinXP 32bit to Win7 32bit, but according to Microsoft's site, they do not support upgrading from 32bit to 64bit. They give the appearance that you will lose any files. – kobaltz Dec 28 '11 at 0:16
Technically, you do lose some files. Mainly your old boot files will be overwritten. – surfasb Dec 28 '11 at 0:30

So I did it,

since the only answer I had was no, I did a backup on a NAS which took hours (that's what I wanted to avoid).

Turns out surfasb was right everything has been put in the Windows.old directory. So it is possible.

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Then you should mark his answer as right – Canadian Luke Dec 28 '11 at 16:20
then he would first need to move his answer from comment to answer – KMC Dec 31 '11 at 5:39

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