[Solved] Old Guest VM Does not start on new Intel CPU Host

[budswell]

Hi,
I had a Centos5x64 guest running on my windows 7 host on my old computer (AMDx2-555). Virtual box 4.2.16
But that computer died. So I now have a new computer (Intel-4670). I have installed Virtual Box 4.3.8
I have checked the BIOS and the VT-x is enabled.
But when I try to start the VM I get the error:

Code: Select all

Your CPU does not support long mode. Use a 32bit distribution

An old Centos6-x32 guest works fine.
I was able to create a new Centos5x64(2) guest and it starts and runs OK.

So am I right in assuming that the old Guest Centos5x64 has some info/drivers/whatever which tied it to the old physical CPU and/or motherboard. And so it won't run on the new computer? Just like a real (not virtual) OS will not run if you change CPU under it?
If so is there any way to fix the guest? Or do I just have to create a new one, and then attach the old virtual disk and copy over my data

Thanks in advance

[socratis]

Disable Hyper-V on your host.

[budswell]

OK figured it out. First time I tried to start it I hadn't enabled VT-x.
This is apparently required for 64bit guests, and it changed the "Version" in the general tab to Ubuntu-32bit. Once I changed this back to Redhat-64bit it all worked.