Can I run a 64-bit VMware image on a 32-bit machine?

The easiest way to check your workstation is to download the VMware Processor Check for 64-Bit Compatibility tool from the VMware website.

You can't run a 64-bit VM session on a 32-bit processor. However, you can run a 64-bit VM session if you have a 64-bit processor but have installed a 32-bit host OS and your processor supports the right extensions. The tool linked above will tell you if yours does.

If you have 32-bit hardware, no, you cannot run a 64-bit guest OS. "VMware software does not emulate an instruction set for different hardware not physically present".

However, QEMU can emulate a 64-bit processor, so you could convert the VMWare machine and run it with this

From this 2008-era blog post (mirrored by archive.org):

$ cd /path/to/vmware/guestos
$ for i in \`ls *[0-9].vmdk\`; do qemu-img convert -f vmdk $i -O raw {i/vmdk/raw};done
$ cat *.raw >> guestos.img

To run it,

qemu -m 256 -hda guestos.img

The downside? Most of us runs VMware without preallocation space for the virtual disk. So, when we make a conversion from VMware to QEMU, the raw file will be the total space WITH preallocation. I am still testing with -f qcow format will it solve the problem or not. Such as:

for i in `ls *[0-9].vmdk`; do qemu-img convert -f vmdk $i -O qcow ${i/vmdk/qcow}; done && cat *.qcow >> debian.img

If your hardware is 32-bit only, then no. If you have 64 bit hardware and a 32-bit operating system, then maybe. See Hardware and Firmware Requirements for 64-Bit Guest Operating Systems for details. It has nothing to do with one vs. multiple processors.

It boils down to whether the CPU in your machine has the the VT bit (Virtualization), and the BIOS enables you to turn it on. For instance, my laptop is a Core 2 Duo which is capable of using this. However, my BIOS doesn't enable me to turn it on.

Note that I've read that turning on this feature can slow normal operations down by 10-12%, which is why it's normally turned off.

I honestly doubt it, for a number of reasons, but the most important one is that there are some instructions that are allowed in 32-bit mode, but not in 64-bit mode. Specifically, the REX prefix that is used to encode some instructions and registers in 64-bit mode is a byte of the form 0x4f:0x40, but in 32 bit mode the same byte is either INC or DEC with a fixed operand.
Because of this, any 64-bit instruction that is prefixed by REX will be interpreted as either INC or DEC, and won't give the VMM the chance to emulate the 64-bit instruction (for instance by signaling an undefined opcode exception).

The only way it might be done is to use a trap exception to return to the VMM after each and every instruction so that it can see if it needs special 64-bit handling. I simply can't see that happening.

VMware? No. However, QEMU has an x86_64 system target that you can use. You likely won't be able to use a VMware image directly (IIRC, there's no conversion tool), but you can install the OS and such yourself and work inside it. QEMU can be a bit of a PITA to get up and running, but it tends to work quite nicely.

VMware does not allow you to run a 64-bit guest on a 32-bit host. You just have to read the documentation to find this out.

If you really want to do this, you can use QEMU, and I recommend a Linux host, but it's going to be very slow (I really mean slow).

Yes, you can. I have a 64-bit Debian running in VMware on Windows XP 32-Bit. As long as you set the Guest to use two processors, it will work just fine.