the nice fact is that citrix xen and virtualbox can use the same/similar PIIX3 controler, which makes moving VMs between them a matter of „how to copy the harddisk sector wise“. (MAKE SHURE VIRTUALBOX IS USING THIS CONTROLER WHEN INSTALLING A NEW WINDOWS(XP/7) VM GOING FROM SATA/AHCI -> TO IDE OR BACK IS A HAL-PAIN! (i read it also helps in win7 to delete the „pci-device“ in hardware manager before backup/moving)
acronis 10 does this job nicely. (get your hands on an acronis 10 boot iso and you are ready to go) my trick was (because acornis has sometimes problems accessing network shares) to add a second virtual harddisk, backup the VM via acronis to this second one. (you can „add disk“ in acronis directly, formating a blank new virtual hd)
acronis 10 DOES WORK under Windows 7, simply RENAME TrueImager.exe to something like TrueImage1.exe and now it starts and works without a problem.
when moving windows 7 xen-VMs be shure to NOT(!) use the default hardware-config that virtualBox is using for Win7 machines, change it to NOT use SATA/AHCI, but PIIX3-IDE.
that’s the whole trick.
(if it still not booting try to disable io-apic)
LINUX (and OSX i guess too) are not so problematic when switching between AHCI and IDE, they simply boot!
default hardware settings in virtualbox for xp:
Citrix Xen 5.6 (and later too i guess) simulates the 82371SB (PIIX3) IDE Controler for all kinds of OS (linux, win xp and win 7).
VirtualBox let’s you choose to either simulate the 82371SB (PIIX3) or PIIX4 or even AHCI (default for win7, but makes it a PAIN in the ASS to move it to IDE, if you want to be save, change default hardware config right after VM creation, BEFORE YOU INSTALL WIN7!)
Oracle says AHCI provides better speeds, so you have to decide what’s more important for you.
So migrating WInXP is a matter of „how do i get my harddisk copied“ which can be done with an acronis true image boot cd or acronis windows installation. (backup to .tib to a network share)
and then restored (again via acronis boot cd) or if that fails by attaching a new vdi to an existing windows + acronis installation and then restoring backup.tib to drive D:
Windows 7 VMs: do not forget to delete VirtualBox’s AHCI SATA Controler and add an PIIX4 storage controler, add the vdi that you restored the backup on to this PIIX4 and everything should boot fine. (not 0x0007B Bluescreen, when changing IDE->AHCI or vice versa)
this is a screenshot from a former citrix xen vm, now running inside VirtualBox. One can cleraly see the Citrix Tools for VIrtual Machines still installed. (should be uninstalled and the guest additions from VB should be installed)