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I have a 32-bit Ubuntu 10.10 as a host OS, VirtualBox 4.0, Windows 7 64-bit Professional as a guest OS. The laptop processor is 64-bit. When I try to load Windows 7 64-bit in VirtualBox, the error appears:

attempting to load a 64-bit application, however this CPU is not compatible with with 64-bit mode

I don't understand, the CPU is compatible with 64-bit mode, what's the problem?

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Please link us your processor name/model. –  Diogo Aug 16 '11 at 18:42
    
You must enable hardware virtualization through your BIOS –  Achu Aug 16 '11 at 18:44
    
Achu, how? I'm trying to google but I cannot find the answer. –  Sergey Aug 16 '11 at 19:00

3 Answers 3

up vote 11 down vote accepted

I believe it's telling you VirtualBox's virtual CPU, though, is not 64-bit compatible. Is hardware virtualization enabled, and have you enabled VirtualBox's 64-bit support for the specific VM in question?

http://www.virtualbox.org/manual/ch03.html#intro-64bitguests

You need a 64-bit processor with hardware virtualization support (see the section called “Hardware vs. software virtualization”).

You must enable hardware virtualization for the particular VM for which you want 64-bit support; software virtualization is not supported for 64-bit VMs.

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VT is disabled in the bios? –  Moab Aug 16 '11 at 18:51
    
Also observe this requirement: "3. If you want to use 64-bit guest support on a 32-bit host operating system, you must also select a 64-bit operating system for the particular VM. Since supporting 64 bits on 32-bit hosts incurs additional overhead, VirtualBox only enables this support upon explicit request." Make sure you select an OS with "(64 bit)" in its name. –  billc.cn Aug 16 '11 at 19:08
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I found it - my processor doesn't support hardware virtualization - that simple –  Sergey Aug 16 '11 at 19:14

It may be because while the CPU supports 64-bit mode, its 64-bit mode is not enabled. Since the host OS is 32-bit, at boot, the CPU is only initialized into its 32-bit mode. So, since the virtualized OS is still using the same CPU as the guest OS, it can only operate in up to 32-bit mode. I believe you likely would have to have the host OS be 64-bit to be able to run the guest OS in 64-bit mode, as well.

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VirtualBox does not require a 64-bit host to create a 64-bit guest –  Mark Sowul Aug 16 '11 at 19:03

Using Oracle VirtualBox, do the following:

  • in VirtualBox settings, go to System, the Motherboard tab, and check the "Enable IO APIC" checkbox
  • also in the BIOS, ensure virtualization technology is enabled. To get there, press F10 (on an HP machine) when powering up your computer to take you to the setup screen (DOS-like background).
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You should read some of the other comments and answers. The author's hardware didn't support what he wanted to do. Furthermore he was using a 32-bit host operating system, and VirtualBox doesn't support a 64-bit operating system on a 32-bit host. –  Ramhound Sep 21 '12 at 11:19
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@Ramhound: Not true. If the processor supports 64-bit operation, 64-bit virtualization is possible, even if the guest operating system is 32-bit. See virtualbox.org/manual/ch03.html#intro-64bitguests –  DragonLord Sep 23 '12 at 2:56

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